**Meet the editors**

Ishaq Ahmad joined the National Centre for Physics in 1999 and currently holds the positions as the director of the Experimental Physics Department, National Centre for Physics, Islamabad, and as an adjunct faculty member of Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad. He has coauthored over 100 publications in SCI journals and supervised several

master's, PhD and postdoctoral degree students. He has published numerous books and book chapters. His research interests focus on ion implantation, radiation-induced modification of materials/nanomaterials, synthesis of nanomaterials/thin films and ion beam analysis of materials. He is an editorial board member and a reviewer of several well-known journals. He was a TWAS-UNESCO-iThemba LABS research associate from 2014 to 2016. He obtained his PhD degree from the University of Chinese Academy of Sciences, China.

Prof. M. Maaza holds his PhD degree in Quantum Neutron Optics from the University of Pierre and Marie Curie and the Commissariat à l'Energie Atomique, respectively. He is currently a permanent joint staff member of the National Research Foundation of South Africa and in charge of the Africa's International Relations desk at iThemba LABS and the University of South

Africa (UNISA). He is the chair of reputed international organizations and commissions. His expertise is in the multidisciplinary field of nanosciences, photonics and solar energy. Within the STI and RDI landscapes, with a Hirsch index of 33, he has published more than 300 ISI international publications and supervised several postgraduates from all over Africa and South Africa.

Contents

**Preface VII**

Chapter 1 **Introductory Chapter: Ion Beam Applications 3** Ishaq Ahmad and Fabian I. Ezema

Chapter 3 **Ion Beams for Materials Analysis: Conventional and Advanced**

Marek E. Schmidt, Masashi Akabori and Hiroshi Mizuta

Sokeng Ifriky Tadadjeu, Balla Diop Ngom, Shane Martin, Robert Ryk

**Section 2 MeV Ion Beam Applications 13**

Elmuez A. Dawi

**Approaches 37**

Chapter 2 **Ion-Nanoscale Matter Interactions 15**

Chapter 4 **Ion Beams for Space Applications 73**

Van Zyl and Malik Maaza

**Section 3 Focused Ion Beam Applications 87**

Tania Tsvetkova

Chapter 6 **Nitrogen Ion Microscopy 113**

Vladimir Egorov and Evgeny Egorov

Chapter 5 **Ion Beams for Nanoscale Optical Data Storage 89**

**Section 1 Introduction 1**

## Contents

#### **Preface XI**

## **Section 4 Ion Implantation 137**

## Chapter 7 **Ion Implantation as a Tool for Controlled Modification of Photoelectrical Properties of Silicon 139** Nina Khuchua, Marina Tigishvili, Nugzar Dolidze, Zurab Jibuti, Revaz Melkadze and Roland Diehl

Preface

dressed in this book.

and patterning.

and recoil atoms numerically.

Ion beam is a well-known versatile tool, which is being used frequently across the world in various applications. This book is aimed to provide a brief introduction of different ap‐

The review in the second part of the book covers the ion beam with the MeV energy range. Furthermore, this book contains the popular research interests regarding the interaction of nanoparticles with MeV-ranged ion beam. Coalescence of nanoparticles to form nanowires with swift heavy ions is discussed in this section. Ion beam in MeV energy range is helping the material scientists to perform material characterization from the last 60 years. Unique and advanced ion beam analysis techniques are also presented in this section. The effects of space radiation on spacecraft body and shielding materials are very severe, sometimes caus‐ ing the operation failure. To overcome these issues, shielding materials are being developed, and ground-based radiation testing of these shielding materials using MeV ion beams is ad‐

The third part of the book defines the recent achievements on focused ion beam generation and its applications. The focused ion beam techniques have been discussed as a novel ap‐ proach for property modification and optimization of wide-bandgap materials for high-den‐ sity data storage application. This section covers focused ion beam application in new digital memory as a data-writing tool in bits of nanometer diameter into new-generation storage materials and photon near-field technology was discussed. Additionally, advance‐ ment in focused ion beam with molecular nitrogen source gas instead of atomic source gases is also discussed here. This new nitrogen focused ion beam source is very useful for imaging

The final segment of the book addressed the most important applications of ion implanter. Ion implantation is one of the key technologies for the fabrication of electronic devices in a controlled manner. Hereby, the modifications of the photoelectrical properties of n-Si and silicon-on-insulator structures due to B+ ion implantation are explained concisely. On the same line, the ion implantation of group V dopants, such as P, As and Sb, in HgCdTe and the computer simulations on the collision of incident ions and lattice atoms are also tried to be incorporated in this book. This approach will help to understand the distributions of ions

The authors are very thankful and want to acknowledge all those who potentially contribute in this book, namely, Prof. Dr. E.A. Dawi, Prof. Dr. V.K. Egorov, Prof. Dr. E.V. Egorov, Prof. Dr. S.I. Tadadjeu, Prof. Dr. B.D. Ngom, Prof. Dr. Shane Martin, Prof. Dr. R.R Van Zyl, Prof.

proaches and recent development in ion beam application. The first section provides a brief introduction into the topic.

## Chapter 8 **Characterization and Simulation of p-Type Ion Implantation in MCT 161** Changzhi Shi

## Preface

**Section 4 Ion Implantation 137**

**VI** Contents

Changzhi Shi

Melkadze and Roland Diehl

**Implantation in MCT 161**

Chapter 8 **Characterization and Simulation of p-Type Ion**

Chapter 7 **Ion Implantation as a Tool for Controlled Modification of Photoelectrical Properties of Silicon 139**

Nina Khuchua, Marina Tigishvili, Nugzar Dolidze, Zurab Jibuti, Revaz

Ion beam is a well-known versatile tool, which is being used frequently across the world in various applications. This book is aimed to provide a brief introduction of different ap‐ proaches and recent development in ion beam application.

The first section provides a brief introduction into the topic.

The review in the second part of the book covers the ion beam with the MeV energy range. Furthermore, this book contains the popular research interests regarding the interaction of nanoparticles with MeV-ranged ion beam. Coalescence of nanoparticles to form nanowires with swift heavy ions is discussed in this section. Ion beam in MeV energy range is helping the material scientists to perform material characterization from the last 60 years. Unique and advanced ion beam analysis techniques are also presented in this section. The effects of space radiation on spacecraft body and shielding materials are very severe, sometimes caus‐ ing the operation failure. To overcome these issues, shielding materials are being developed, and ground-based radiation testing of these shielding materials using MeV ion beams is ad‐ dressed in this book.

The third part of the book defines the recent achievements on focused ion beam generation and its applications. The focused ion beam techniques have been discussed as a novel ap‐ proach for property modification and optimization of wide-bandgap materials for high-den‐ sity data storage application. This section covers focused ion beam application in new digital memory as a data-writing tool in bits of nanometer diameter into new-generation storage materials and photon near-field technology was discussed. Additionally, advance‐ ment in focused ion beam with molecular nitrogen source gas instead of atomic source gases is also discussed here. This new nitrogen focused ion beam source is very useful for imaging and patterning.

The final segment of the book addressed the most important applications of ion implanter. Ion implantation is one of the key technologies for the fabrication of electronic devices in a controlled manner. Hereby, the modifications of the photoelectrical properties of n-Si and silicon-on-insulator structures due to B+ ion implantation are explained concisely. On the same line, the ion implantation of group V dopants, such as P, As and Sb, in HgCdTe and the computer simulations on the collision of incident ions and lattice atoms are also tried to be incorporated in this book. This approach will help to understand the distributions of ions and recoil atoms numerically.

The authors are very thankful and want to acknowledge all those who potentially contribute in this book, namely, Prof. Dr. E.A. Dawi, Prof. Dr. V.K. Egorov, Prof. Dr. E.V. Egorov, Prof. Dr. S.I. Tadadjeu, Prof. Dr. B.D. Ngom, Prof. Dr. Shane Martin, Prof. Dr. R.R Van Zyl, Prof. Dr. Tania Tsvetkova, Prof. Dr. Marek E. Schmidt, Prof. Dr. Masashi Akabori, Prof. Dr. Hir‐ oshi Mizuta, Prof. Dr. Nina Khuchua, Prof. Dr. Marina Tigishvili, Prof. Dr. Nugzar Dolidze, Prof. Dr. Zurab Jibuti, Prof. Dr. Revaz Melkadze, Prof. Dr. Roland Diehl, Prof. Dr. Changzhi Shi and Mr. Julian Virag, Publishing Process Manager.

Regards

**Ishaq Ahmad** National Centre for Physics Islamabad, Pakistan

#### **Malik Maaza**

**Introduction**

**Section 1**

UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology UNISA and Nanosciences African Network iThemba LABS-National Research Foundation South Africa

**Section 1**

## **Introduction**

Dr. Tania Tsvetkova, Prof. Dr. Marek E. Schmidt, Prof. Dr. Masashi Akabori, Prof. Dr. Hir‐ oshi Mizuta, Prof. Dr. Nina Khuchua, Prof. Dr. Marina Tigishvili, Prof. Dr. Nugzar Dolidze, Prof. Dr. Zurab Jibuti, Prof. Dr. Revaz Melkadze, Prof. Dr. Roland Diehl, Prof. Dr. Changzhi

**Ishaq Ahmad**

**Malik Maaza**

South Africa

Islamabad, Pakistan

National Centre for Physics

UNISA and Nanosciences African Network iThemba LABS-National Research Foundation

UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology

Shi and Mr. Julian Virag, Publishing Process Manager.

Regards

VIII Preface

**Chapter 1**

**Provisional chapter**

**Introductory Chapter: Ion Beam Applications**

**Introductory Chapter: Ion Beam Applications**

DOI: 10.5772/intechopen.78966

Ion beam instruments such as particle accelerators, focused ion beams (FIB), and ion implanters are versatile instruments which are broadly applied almost in all field of physics from nuclear physics to particle physics, condense matter physics, and atomic physics. These are also an important tool in other areas of science and technologies such as chemistry, environment sciences, biology, space science and engineering, and semiconductor technology. Its applications are substantially being extended for generating cluster ions, synchrotron radiations, focused ion beams with molecular nitrogen source gas, and proton-proton colliders. Progress in nuclear and particle physics originated from studies with ion beam is playing now a determining role in astrophysics and cosmology. Similarly, low energy ion beam, such as ion implanters and FIB, are also useful instruments for device fabrication and

This chapter aimed to present a brief review of a broad range of applications of the ion beam in diversified fields which will be useful for the common reader to understand ion beam science and technology. Finally, the latest research using MeV ion beam, focused ion beam, and ion implanter is compiled in this book in three respective sections. For a further concise review of ion beam applications, electron beams are excluded from this review chapter and book, even though electron microscopes and other useful applications are being emerged in different areas of fields. For example, focused electron beam was used in patterning and cutting of nanowires [1]. **Figure 1** shows the patterning of ZnO nanowires

using focused electron beams at transmission electron microscopy (TEM).

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Ishaq Ahmad and Fabian I. Ezema

http://dx.doi.org/10.5772/intechopen.78966

**1. Overview**

microscopy.

Additional information is available at the end of the chapter

Ishaq Ahmad and Fabian I. EzemaAdditional information is available at the end of the chapter

#### **Introductory Chapter: Ion Beam Applications Introductory Chapter: Ion Beam Applications**

DOI: 10.5772/intechopen.78966

Ishaq Ahmad and Fabian I. Ezema

Additional information is available at the end of the chapter Ishaq Ahmad and Fabian I. EzemaAdditional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78966

## **1. Overview**

Ion beam instruments such as particle accelerators, focused ion beams (FIB), and ion implanters are versatile instruments which are broadly applied almost in all field of physics from nuclear physics to particle physics, condense matter physics, and atomic physics. These are also an important tool in other areas of science and technologies such as chemistry, environment sciences, biology, space science and engineering, and semiconductor technology. Its applications are substantially being extended for generating cluster ions, synchrotron radiations, focused ion beams with molecular nitrogen source gas, and proton-proton colliders. Progress in nuclear and particle physics originated from studies with ion beam is playing now a determining role in astrophysics and cosmology. Similarly, low energy ion beam, such as ion implanters and FIB, are also useful instruments for device fabrication and microscopy.

This chapter aimed to present a brief review of a broad range of applications of the ion beam in diversified fields which will be useful for the common reader to understand ion beam science and technology. Finally, the latest research using MeV ion beam, focused ion beam, and ion implanter is compiled in this book in three respective sections. For a further concise review of ion beam applications, electron beams are excluded from this review chapter and book, even though electron microscopes and other useful applications are being emerged in different areas of fields. For example, focused electron beam was used in patterning and cutting of nanowires [1]. **Figure 1** shows the patterning of ZnO nanowires using focused electron beams at transmission electron microscopy (TEM).

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

implant required elements into required depth to make semiconductor devices. Section 3 describes the advantages of ion implantation process with emerging new applications.

Introductory Chapter: Ion Beam Applications http://dx.doi.org/10.5772/intechopen.78966 5

Focused ion beam in keV energies is also used for microscopy of materials [12]. FIB instrument can be utilized for microstructure tomography in the range from ∼100 nm to 10 μm.

IBA techniques such as PIXE are widely used for environmental studies. Trace element measurement in aerosol samples is an important application of MeV ion beam. After developed microprobe, now it is possible to measure or mapping of heavy metals in various samples like trees, fish, deposit mining dust on trees leaf, glacial melting study, etc., which give valuable seasonal and historical information of pollution to the particular area of study. Many authors have proven the diagnostic usefulness of hair analysis in assessing pathological elemental concentrations in the body. Hair has been shown to reflect environmental and occupational exposure to lead, mercury, aluminum [13], and a combination of multiple metals. Microanalysis of hair to assess the toxic metals in scalp hair of artisanal miners are important environmental studies using micro PIXE. The PIXE technique has been proven as a high accurate, sensitive, and nondestructive method to determine concentration and composition of chemical elements. Beside these, PIXE technique has been successfully used in many other environmental studies like elemental mapping, source appointment, and chemical character-

Focused ion beam either in MeV or keV energies is a considerable tool in science and technology for micro and nanodevice fabrications using both bottom-up and top-down approaches. In the bottom-up approach, individual nano-objects such as nanowires and nanotubes can be assembled directly together in form of functional welded networks using ion beam induced nano-welding technique. Ion beam-induced nanowelding is another option to make nanowire/nanotube-welded junctions and to make nanodevices or integrate nanodevices. Recently, researchers used ion beam as a tool to weld carbon nanotubes, silver nanowires, Ni nanowires, and SiC nanowires to make junctions and large-scale welded networks [14–21] (**Figure 2**).

In top-down device fabrication approach, 3D MeV proton beam writing is an important technique to make micro and nanodevices [22]. Whereas, keV energy FIB is now an essential tool to use for TEM sample preparation and device fabrication and to fabricate complex nanoscale structures/patterns. It is a tool that directly makes a 3D and 2D pattern without masks from a few nanometers to hundreds of micrometers in size. Compact FIB instruments are developed and being used to fabricate microelectromechanical systems (MEMS)-based devices, microfluidic chips, photonic devices, and DNA sequencing nanopore membranes [23, 24]. More

Advanced FIB microscopy has been described in detail in Section 3.

**2.2. Environmental sciences**

ization of various pollutants.

detail FIB applications are described in Section 3.

**2.3. Device fabrications**

**Figure 1.** Focused electron beam to create nanoholes in ZnO nanowires [1].

## **2. Applications**

## **2.1. Materials science**

This section introduces to the materials scientists, chemists, and physicists about the ion beam techniques for materials analysis, modification of materials, and development of new materials using ion beam. MeV ion beams for materials analysis techniques are being used as complementary techniques in materials analysis. These are the group of non-destructive analytical techniques such as particle induced X-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), nuclear reaction analysis (NRA), Rutherford backscattering (RBS), and ion channeling, which are being used to analyze composition and depth profiling of solids. Almost all elements from hydrogen onward can be probed by ion beam analysis (IBA). IBA techniques are discussed in detail in Section 2. Focused or collimated beam into micron and submicron (Microprobe) is now developed, which is useful for mapping of lateral elemental distribution over a specimen. These microbeams are useful for high-resolution imaging by measuring density variations through scanning transmission ion microscopy (STIM) technique.

Ion beam modification of materials is an important application of ion beam. Recently, boron carbonitride nanotubes were synthesized from boron nitride nanotubes using C ion beam irradiation [2]. Similarly, phase transformation of thin film and nanostructured materials by ion beams is another important application. Ion beam-induced controlled modification of physical properties is possible in thin film and nanostructured materials [2–8]. Phase segregation and separation is another unique application of ion beam [9].

Ion implantation is an exceptional surface treatment method to implant N-type and P-type dopants into semiconductors to make solid-state electronics. Moreover, dilute magnetic semiconductor devices could be synthesized through direct implantation of magnetic elements into nonmagnetic semiconductors [10, 11]. After developed FIB, now it is also possible to implant required elements into required depth to make semiconductor devices. Section 3 describes the advantages of ion implantation process with emerging new applications.

Focused ion beam in keV energies is also used for microscopy of materials [12]. FIB instrument can be utilized for microstructure tomography in the range from ∼100 nm to 10 μm. Advanced FIB microscopy has been described in detail in Section 3.

## **2.2. Environmental sciences**

IBA techniques such as PIXE are widely used for environmental studies. Trace element measurement in aerosol samples is an important application of MeV ion beam. After developed microprobe, now it is possible to measure or mapping of heavy metals in various samples like trees, fish, deposit mining dust on trees leaf, glacial melting study, etc., which give valuable seasonal and historical information of pollution to the particular area of study. Many authors have proven the diagnostic usefulness of hair analysis in assessing pathological elemental concentrations in the body. Hair has been shown to reflect environmental and occupational exposure to lead, mercury, aluminum [13], and a combination of multiple metals. Microanalysis of hair to assess the toxic metals in scalp hair of artisanal miners are important environmental studies using micro PIXE. The PIXE technique has been proven as a high accurate, sensitive, and nondestructive method to determine concentration and composition of chemical elements. Beside these, PIXE technique has been successfully used in many other environmental studies like elemental mapping, source appointment, and chemical characterization of various pollutants.

## **2.3. Device fabrications**

**2. Applications**

4 Ion Beam Applications

**2.1. Materials science**

This section introduces to the materials scientists, chemists, and physicists about the ion beam techniques for materials analysis, modification of materials, and development of new materials using ion beam. MeV ion beams for materials analysis techniques are being used as complementary techniques in materials analysis. These are the group of non-destructive analytical techniques such as particle induced X-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), nuclear reaction analysis (NRA), Rutherford backscattering (RBS), and ion channeling, which are being used to analyze composition and depth profiling of solids. Almost all elements from hydrogen onward can be probed by ion beam analysis (IBA). IBA techniques are discussed in detail in Section 2. Focused or collimated beam into micron and submicron (Microprobe) is now developed, which is useful for mapping of lateral elemental distribution over a specimen. These microbeams are useful for high-resolution imaging by measuring

density variations through scanning transmission ion microscopy (STIM) technique.

tion and separation is another unique application of ion beam [9].

**Figure 1.** Focused electron beam to create nanoholes in ZnO nanowires [1].

Ion beam modification of materials is an important application of ion beam. Recently, boron carbonitride nanotubes were synthesized from boron nitride nanotubes using C ion beam irradiation [2]. Similarly, phase transformation of thin film and nanostructured materials by ion beams is another important application. Ion beam-induced controlled modification of physical properties is possible in thin film and nanostructured materials [2–8]. Phase segrega-

Ion implantation is an exceptional surface treatment method to implant N-type and P-type dopants into semiconductors to make solid-state electronics. Moreover, dilute magnetic semiconductor devices could be synthesized through direct implantation of magnetic elements into nonmagnetic semiconductors [10, 11]. After developed FIB, now it is also possible to Focused ion beam either in MeV or keV energies is a considerable tool in science and technology for micro and nanodevice fabrications using both bottom-up and top-down approaches. In the bottom-up approach, individual nano-objects such as nanowires and nanotubes can be assembled directly together in form of functional welded networks using ion beam induced nano-welding technique. Ion beam-induced nanowelding is another option to make nanowire/nanotube-welded junctions and to make nanodevices or integrate nanodevices. Recently, researchers used ion beam as a tool to weld carbon nanotubes, silver nanowires, Ni nanowires, and SiC nanowires to make junctions and large-scale welded networks [14–21] (**Figure 2**).

In top-down device fabrication approach, 3D MeV proton beam writing is an important technique to make micro and nanodevices [22]. Whereas, keV energy FIB is now an essential tool to use for TEM sample preparation and device fabrication and to fabricate complex nanoscale structures/patterns. It is a tool that directly makes a 3D and 2D pattern without masks from a few nanometers to hundreds of micrometers in size. Compact FIB instruments are developed and being used to fabricate microelectromechanical systems (MEMS)-based devices, microfluidic chips, photonic devices, and DNA sequencing nanopore membranes [23, 24]. More detail FIB applications are described in Section 3.

X-ray production cross section of particular shell using fluorescence yield of shell of target element. For K-shell, X-ray production cross-section data are available so far to support PIXE technique for materials analysis, whereas a lot of discrepancies exist in L-shell and M-shell of X-ray production cross section measurement. As it had become complicated due to fluores-

Introductory Chapter: Ion Beam Applications http://dx.doi.org/10.5772/intechopen.78966 7

The fine and hyperfine lines originating from s, p, d and f orbitals and its suborbitals (from levels and sublevel) can be studied and explore the fluorescence and auger electron transition and Coster-Kronig transition for L- and M-shell X-ray production cross section. The relative intensity ratios of K-shell, L-shell, and M-shell transition lines can be explored from light and heavy ion in advanced studies. Decreasing and increasing trend of intensity ratio of transitions lines Kα/Kβ and Lβ/Lα can also be explored as a function of ascending order of elements

The stopping power or energy loss of projectile in the matter is another research area. Due to lack of correct knowledge of stopping power, error in cross-section measurement is large. Bethe formalism and Ziegler, the founder of TRIM/SRIM software for heavy ions stopping power, may deviate from the experimental results at different energy ranges. The study reveals that there are many discrepancies exist in the theoretical models. Using heavy ion for

The multi-ionization effect by heavy ion is an open research field and a once need to explore the complicated physics exit behind it. PIXE using heavy ion lead us to find the fact for cor-

Study of nuclear structure and nuclear reaction using ion beam is another application of ion beam technology. As the diameter of the nucleus is less than 10−14 m, the nuclear structure study with microscopy technique is hard to investigate. Therefore, high energy ions which have a size comparable to a nucleus are another option to investigate the structure of the nucleus. Scattering cross section could be measured by energetic ions interacting with target nucleus. Ion-induced nuclear reaction could be possible to emit secondary particles such as neutrons, alpha particle, gamma-rays, and beta particles. Once energies and angular distribution of secondary particle emission observe, then size and shape of the nucleus and the forces existing inside the nucleus could be deduced. Large range of ion beam-induced nuclear reac-

Proton beams with different energies are very useful for various aspects of research, such as proton beams with energies between 1 MeV and 1 GeV are almost always used for nuclear structure studies. Proton beam with energy between 1 and 100 MeV could be made to interact with whole nuclei or with several nucleons, while proton beam with energy between 100 and 1000 MeV could be interacted with individual nucleons in the nucleus which giving more precise information about each nucleon. Ion beam energies greater than 1 GeV are useful to

cross section and stopping power studies can improve the theoretical models.

cence and auger electron transition between levels and sublevels.

Z, respectively.

rections of theoretical Models.

**2.5. Nuclear physics**

tions is possible.

produce short-lived particles such as mesons [25].

**Figure 2.** Ion beam-induced welding of (a) multiwalled carbon nanotubes [21], (b) SiC nanowires [14], (c) Cu nanowires, and (d) silver nanowires [18].

#### **2.4. Atomic physics**

Excitation and ionization of atoms by ion beam is another application of ion beam technology to study atomic structure. Ion beam-induced X-ray emission is a rich phenomenon to study the complicated process during ion beam interaction with matter. The fundamental parameter such as ionization cross section is a pure quantum mechanical phenomenon. When an ion passes through the target atom, the target atom becomes ionized due to columbic interaction of ions with target atom. The target atom is ionized by absorbing ion beam energy and rest of the energy is utilized in ejaculation of auger electron in case of atomic collision and heating.

When an atom deionized, it released the absorbed energy in the form of photon, and its excess energy ejaculates the auger electron and rest of the energy loss goes in the heating of sample. The probability of emission of x-rays or photon from particular due to electron transition from upper shell to lower shell is called the fluorescence of particular shell. We can measure the X-ray production cross section of particular shell using fluorescence yield of shell of target element. For K-shell, X-ray production cross-section data are available so far to support PIXE technique for materials analysis, whereas a lot of discrepancies exist in L-shell and M-shell of X-ray production cross section measurement. As it had become complicated due to fluorescence and auger electron transition between levels and sublevels.

The fine and hyperfine lines originating from s, p, d and f orbitals and its suborbitals (from levels and sublevel) can be studied and explore the fluorescence and auger electron transition and Coster-Kronig transition for L- and M-shell X-ray production cross section. The relative intensity ratios of K-shell, L-shell, and M-shell transition lines can be explored from light and heavy ion in advanced studies. Decreasing and increasing trend of intensity ratio of transitions lines Kα/Kβ and Lβ/Lα can also be explored as a function of ascending order of elements Z, respectively.

The stopping power or energy loss of projectile in the matter is another research area. Due to lack of correct knowledge of stopping power, error in cross-section measurement is large. Bethe formalism and Ziegler, the founder of TRIM/SRIM software for heavy ions stopping power, may deviate from the experimental results at different energy ranges. The study reveals that there are many discrepancies exist in the theoretical models. Using heavy ion for cross section and stopping power studies can improve the theoretical models.

The multi-ionization effect by heavy ion is an open research field and a once need to explore the complicated physics exit behind it. PIXE using heavy ion lead us to find the fact for corrections of theoretical Models.

## **2.5. Nuclear physics**

**2.4. Atomic physics**

6 Ion Beam Applications

and (d) silver nanowires [18].

Excitation and ionization of atoms by ion beam is another application of ion beam technology to study atomic structure. Ion beam-induced X-ray emission is a rich phenomenon to study the complicated process during ion beam interaction with matter. The fundamental parameter such as ionization cross section is a pure quantum mechanical phenomenon. When an ion passes through the target atom, the target atom becomes ionized due to columbic interaction of ions with target atom. The target atom is ionized by absorbing ion beam energy and rest of the energy is utilized in ejaculation of auger electron in case of atomic collision and heating. When an atom deionized, it released the absorbed energy in the form of photon, and its excess energy ejaculates the auger electron and rest of the energy loss goes in the heating of sample. The probability of emission of x-rays or photon from particular due to electron transition from upper shell to lower shell is called the fluorescence of particular shell. We can measure the

**Figure 2.** Ion beam-induced welding of (a) multiwalled carbon nanotubes [21], (b) SiC nanowires [14], (c) Cu nanowires,

Study of nuclear structure and nuclear reaction using ion beam is another application of ion beam technology. As the diameter of the nucleus is less than 10−14 m, the nuclear structure study with microscopy technique is hard to investigate. Therefore, high energy ions which have a size comparable to a nucleus are another option to investigate the structure of the nucleus. Scattering cross section could be measured by energetic ions interacting with target nucleus. Ion-induced nuclear reaction could be possible to emit secondary particles such as neutrons, alpha particle, gamma-rays, and beta particles. Once energies and angular distribution of secondary particle emission observe, then size and shape of the nucleus and the forces existing inside the nucleus could be deduced. Large range of ion beam-induced nuclear reactions is possible.

Proton beams with different energies are very useful for various aspects of research, such as proton beams with energies between 1 MeV and 1 GeV are almost always used for nuclear structure studies. Proton beam with energy between 1 and 100 MeV could be made to interact with whole nuclei or with several nucleons, while proton beam with energy between 100 and 1000 MeV could be interacted with individual nucleons in the nucleus which giving more precise information about each nucleon. Ion beam energies greater than 1 GeV are useful to produce short-lived particles such as mesons [25].

## **2.6. Biology**

Ion beam could be applied in biology for probing, damaging and modifying the biological samples. Ion beam accelerators have advanced further by the introduction of nuclear microprobes. These microprobes have opened up new areas of research in biological science by allowing elemental microanalysis, with imaging capabilities, particularly suitable for the measurement of trace elements in biological tissues. Whereas ion beam-induced mutation of crops, vegetables and fruits are matured method. Micro PIXE is continuously applied in life science for comprehensive food crops analysis to determine traces of toxic heavy metals.

damage to the surrounding uninfected tissues. Radiotherapy with carbon ion beam is also developed and is popular in the world, while heavy ion therapy research is going on by understanding fundamental damage mechanisms of cancer cells under heavy ion irradiation [26].

Introductory Chapter: Ion Beam Applications http://dx.doi.org/10.5772/intechopen.78966 9

The production of radioactive ion beam and studying its properties are currently a hot research area in accelerator scientific community and for nuclear astrophysicists. Energetic radioactive ion beam, a beam of short-lived nuclei, opens up a new research direction to study nuclear reactions and nuclear structures. Nuclear reaction with radioactive ion beam provides information on reactions that occur at our sun and other stars in our universe. For astrophysics point of view, scientists have produced short-lived halo nuclei in radioactive ion beam facilities to study nuclear astrophysics. Further research is going on for a generation of short-lived neutron-enriched nuclei in next-generation radioactive ion beam facilities, which are required to understand the existence of heavy elements in the universe by the astrophysics rapid neutron-capture process. Through this short-lived radioactive ion beam, it may be possible to explore the secrets of the universe as these nuclei beams play a vital role in understanding the origin of the elements and the dynamics of stellar objects. Moreover, short-lived nuclei (radioactive ion beam) are essential for useful studies of astrophysical objects such as neutron stars, super novae, X-ray bursters, and supernovae. In conclusion, short-lived halo nuclei in radioactive ion beam facilities will provide us with the information that how the chemical elements had formed our

Recent researches in ion beam applications that are mentioned in this introductory chapter are so detailed that it is not possible to cover them in this book. Therefore, this book only has

selected special chapters from distinguished authors that cover various aspects of:

2 Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria

**2.9. Nuclear astrophysics**

world in the cosmos [27].

**1.** MeV ion beam applications

**2.** Focused ion beam applications

\* and Fabian I. Ezema2 \*Address all correspondence to<EMAIL_ADDRESS>1 National Centre for Physics, Islamabad, Pakistan

**3. Conclusion**

**3.** Ion implantation

**Author details**

Ishaq Ahmad<sup>1</sup>

## **2.7. Particle physics**

High-energy ion beams produced by particle accelerators also have vast applications in particle physics as it is a tool to study extreme states of matter. In high energy physics, particle colliders have taken part in a key role in scientific discoveries for last many decades. Particle colliders are basically ion beam accelerators where particles are accelerated up to relativistic speed to collide with a stationary target or head-on collision with each other like protonproton colliders. At sufficiently high energy, relativistic particles smash into other high energy particles. Energies of the colliders continuously increase over time for exploring new physics/particles. Moreover, advanced high energy particle detectors are being developed for understanding the properties of high energy particles such as mass, energy, charge, spin, and isospin, which are being created during collision of relativistic particles.

Large Hadron Collider (LHC) is the world's largest accelerator built at Swiss-French border in Geneva, Switzerland. It is also used to accelerate the heavy ion beams. It is capable of accelerating Pb ions with the beam energy of 2.76 TeV/nucleon, which yield to 1.15 PeV in total, with the luminosity of 1.0 × 1027 cm−2 s−1. Heavy ion beam focuses on study of quantumchromo-dynamics (QCD), the strong interaction sector of Standard Model (SM). It allows to study physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collision.

## **2.8. Medical application**

Medical radioisotopes for medical applications are well established for diagnostic and therapy. Ion beams are also being used to produce radioisotopes that are used for the mentioned uses. Further research is also going on to produce high-quality radioisotopes through the series of investigation into production of radioisotopes and its decay characteristics in medical applications such as cross-section measurement of ion beam with target atom to monitor nuclear reactions, compilation of nuclear reaction data for therapeutic radionuclides production, and Beta decay nuclear reaction cross-section measurement for positron emission tomography.

Ion beam therapy is another unique application of ion beam, which provides cutting-edge cancer treatment. Ion beam therapy is a newly emerging treatment for cancer, which is more effective than any other old techniques. In ion beam therapy, ion beam is offering the possibility of excellent dose localization and thus maximizing cell killing within the tumor. Proton therapy for cancer treatment is a matured technology to damage cancer cells while producing the least damage to the surrounding uninfected tissues. Radiotherapy with carbon ion beam is also developed and is popular in the world, while heavy ion therapy research is going on by understanding fundamental damage mechanisms of cancer cells under heavy ion irradiation [26].

## **2.9. Nuclear astrophysics**

**2.6. Biology**

8 Ion Beam Applications

**2.7. Particle physics**

**2.8. Medical application**

tomography.

Ion beam could be applied in biology for probing, damaging and modifying the biological samples. Ion beam accelerators have advanced further by the introduction of nuclear microprobes. These microprobes have opened up new areas of research in biological science by allowing elemental microanalysis, with imaging capabilities, particularly suitable for the measurement of trace elements in biological tissues. Whereas ion beam-induced mutation of crops, vegetables and fruits are matured method. Micro PIXE is continuously applied in life science for comprehensive food crops analysis to determine traces of toxic heavy metals.

High-energy ion beams produced by particle accelerators also have vast applications in particle physics as it is a tool to study extreme states of matter. In high energy physics, particle colliders have taken part in a key role in scientific discoveries for last many decades. Particle colliders are basically ion beam accelerators where particles are accelerated up to relativistic speed to collide with a stationary target or head-on collision with each other like protonproton colliders. At sufficiently high energy, relativistic particles smash into other high energy particles. Energies of the colliders continuously increase over time for exploring new physics/particles. Moreover, advanced high energy particle detectors are being developed for understanding the properties of high energy particles such as mass, energy, charge, spin, and

Large Hadron Collider (LHC) is the world's largest accelerator built at Swiss-French border in Geneva, Switzerland. It is also used to accelerate the heavy ion beams. It is capable of accelerating Pb ions with the beam energy of 2.76 TeV/nucleon, which yield to 1.15 PeV in total, with the luminosity of 1.0 × 1027 cm−2 s−1. Heavy ion beam focuses on study of quantumchromo-dynamics (QCD), the strong interaction sector of Standard Model (SM). It allows to study physics of strongly interacting matter and the quark-gluon plasma at extreme values of

Medical radioisotopes for medical applications are well established for diagnostic and therapy. Ion beams are also being used to produce radioisotopes that are used for the mentioned uses. Further research is also going on to produce high-quality radioisotopes through the series of investigation into production of radioisotopes and its decay characteristics in medical applications such as cross-section measurement of ion beam with target atom to monitor nuclear reactions, compilation of nuclear reaction data for therapeutic radionuclides production, and Beta decay nuclear reaction cross-section measurement for positron emission

Ion beam therapy is another unique application of ion beam, which provides cutting-edge cancer treatment. Ion beam therapy is a newly emerging treatment for cancer, which is more effective than any other old techniques. In ion beam therapy, ion beam is offering the possibility of excellent dose localization and thus maximizing cell killing within the tumor. Proton therapy for cancer treatment is a matured technology to damage cancer cells while producing the least

isospin, which are being created during collision of relativistic particles.

energy density and temperature in nucleus-nucleus collision.

The production of radioactive ion beam and studying its properties are currently a hot research area in accelerator scientific community and for nuclear astrophysicists. Energetic radioactive ion beam, a beam of short-lived nuclei, opens up a new research direction to study nuclear reactions and nuclear structures. Nuclear reaction with radioactive ion beam provides information on reactions that occur at our sun and other stars in our universe. For astrophysics point of view, scientists have produced short-lived halo nuclei in radioactive ion beam facilities to study nuclear astrophysics. Further research is going on for a generation of short-lived neutron-enriched nuclei in next-generation radioactive ion beam facilities, which are required to understand the existence of heavy elements in the universe by the astrophysics rapid neutron-capture process. Through this short-lived radioactive ion beam, it may be possible to explore the secrets of the universe as these nuclei beams play a vital role in understanding the origin of the elements and the dynamics of stellar objects. Moreover, short-lived nuclei (radioactive ion beam) are essential for useful studies of astrophysical objects such as neutron stars, super novae, X-ray bursters, and supernovae. In conclusion, short-lived halo nuclei in radioactive ion beam facilities will provide us with the information that how the chemical elements had formed our world in the cosmos [27].

## **3. Conclusion**

Recent researches in ion beam applications that are mentioned in this introductory chapter are so detailed that it is not possible to cover them in this book. Therefore, this book only has selected special chapters from distinguished authors that cover various aspects of:

## **Author details**

Ishaq Ahmad<sup>1</sup> \* and Fabian I. Ezema2

\*Address all correspondence to<EMAIL_ADDRESS>

## **References**

[1] Ahmad I, Dee CF, Husnain G, Rafique HM, Yan L, Naseem S. The use of high intensity electron beam to form nanohole, induce bending and fabricate nano-contact on a ZnO nanowire. Micro and Nano Letters. 2012;**7**:122-124

[14] Khan R, Khan MAR, Ahmad I, Khan MA, Iqbal T, Ezema FI, Maaza M. Joining of individual silicon carbide nanowires via proton beam irradiation. Current Nanoscience.

[15] Honey S, Naseem S, Ahmad I, Maaza M, Bhatti MT, Madhuku M.Interconnections between Ag-NWs build by argon ions beam irradiation. Journal of Nanomaterials & Molecular

[16] Honey S, Ishaq I, Madhuku M, Naseem S, Maaza M, Kennedy JV. Nickel nanowires mesh fabricated by ion beam irradiation-induced nanoscale welding for transparent

[17] Shehla H, Naseem S, Ishaq A, Maaza M, Bhatti MT, Wan D. Large scale silver nanow-

[18] Shehla H, Ishaq A, Yaqoob K, Javed I, Saira R, Shahzad N, Maaza M. Ion beam irradiation-induced nano-welding of Ag nanowires. Micro and nano Letters. 2016;**11**:34-37

[19] Shehla H, Khan S, Javed I, Madhuku M, Ahmad I, Shahzad N, Maaza M. Protons irradiation induced coalescence of silver nanowires. Current Nanoscience. 2015;**11**:792-796 [20] Ishaq A, Ni Z, Long Yan L, Gong J, Zhu D. Constructing carbon nanotube junctions by

[21] Ishaq A, Yan L, Zhu D. The electrical conductivity of carbon nanotube sheets by ion beam irradiation. NuclearInstruments and Methods in Physics Research B. 2009;**267**:1779-1782

[22] Sum TC, Bettiol AA, Kan JA, Watt F, Pun EYB, Tung KK. Proton beam writing of low-loss

[23] Steve R, Robert P. A review of focused ion beam applications in microsystem technol-

[24] Chih JL, Thomas A, Alexey B. Fabrication of symmetric sub-5 nm nanopores using

[25] Clark DJ. Accelerators for nuclear physics. Reports on Progress in Physics. 1972;**35**:

[26] Hirohiko T. Overview of carbon-ion radiotherapy. Journal of Physics: Conference Series.

[27] Karlheinz L, Hendrik S. The role of radioactive ion beams in nuclear astrophysics.

Ar ion beam irradiation. Radiation Physics and Chemistry. 2010;**79**:687-691

polymer optical waveguides. Applied Physics Letters. 2013;**83**:1707-1709

ogy. Journal of Micromechanics and Microengineering. 2001;**11**:287-300

focused ion and electron beams. Nanotechnology. 2006;**17**:3264-3267

) ion beam irradiation. Chinese Physics B.

Introductory Chapter: Ion Beam Applications http://dx.doi.org/10.5772/intechopen.78966 11

2018;**14**:1-6. DOI: 10.2174/1573413714666180328153514

ires network fabricated by MeV hydrogen (H+

conducting electrodes. Materials Research Express. 2017;**4**:075042

Nanotechnology. 2017;**6**:1000213

2016;**25**:046105

1007-1075

2017;**777**:012032

Physica Scripta. 2013;**T152**:014011

[14] Khan R, Khan MAR, Ahmad I, Khan MA, Iqbal T, Ezema FI, Maaza M. Joining of individual silicon carbide nanowires via proton beam irradiation. Current Nanoscience. 2018;**14**:1-6. DOI: 10.2174/1573413714666180328153514

**References**

10 Ion Beam Applications

TiO2

2013;**27**:1350020

[1] Ahmad I, Dee CF, Husnain G, Rafique HM, Yan L, Naseem S. The use of high intensity electron beam to form nanohole, induce bending and fabricate nano-contact on a ZnO

[2] Ahmad I, Naqvi SR, Iqbal JI, Lu B, Yan L, Dee CF, Aslam B. Substitutional carbon doping of hexagonal multiwalled boron nitride nanotubes (h-MWBNNTs) via ion implantation.

[3] Bushra B, Shehla H, Madhuku M, Ahmad I, Khan R, Arshad M, Alamgir K, Naseem S, Maaza M. MeV carbon ion irradiation-induced changes in the electrical conductivity of

[4] Usman M, Naeem M, Hassan NU, Maqbool M, Iftikhar A, Ahmad I, Zahid H. Structural, optical, and electrical characteristics of AlN:Ho thin films irradiated with 700 keV pro-

[5] Ishfaq M, Rizwan Khan M, Bhopal MF, Nasim F, Ali A, Bhatti AS, Ahmad I, Bhardwaj S, Cepek C. 1.5 MeV proton irradiation effects on electrical and structural properties of

[6] Khan S, Husnain G, Ahmad I, Khan K, Usman M, Saira R. Structural characteristics of

[7] Shah A, Husnain G, Ahmad I, Arshad M. Cu ions irradiation impact on structural and optical properties of GaN thin film. International Journal of Modern Physics B.

[8] Yan L, Zhou G, Ahmad I, Zhou X. Improving the electrical conductivity of multi-walled carbon nanotube networks by H ion beam irradiation. Carbon. 2011;**49**:2141-2144

[9] Ahmad I, Madhuku M, Adeela S, Khan S, Javaid H, Ali A, Wang D, Ilyas SZ, Mola G, Waheed A, Rasheed MA. Tailoring the structural and optical characteristics of InGaN/GaN multilayer thin films by 12 MeV Si ion irradiation. Materials Science in

[10] Husnain G, Yao SD, Ahmad I, Arshad RHM, M M. Characterization of n-GaN dilute magnetic semiconductors by cobalt ions implantation at high-fluence. Journal of

[11] Husnain G, Yao SD, Ahmad I, Rafique HM. Structural and magnetic impact of Cr+−

[12] Munroe PR. The application of focused ion beam microscopy in the material sciences.

[13] Kempson IM, Lombi E. Hair analysis as a biomonitor for toxicology, disease and health

implantation into GaN thin film. Solid State Sciences. 2012;**14**:735-738

silver nanowire networks. Current Applied Physics. 2015;**15**:642-647

/n-Si interface. Journal of Applied Physics. 2014;**115**:174506

nanowire. Micro and Nano Letters. 2012;**7**:122-124

Journal of Nanoparticle Research. 2014;**16**:2170-2178

tons. Applied Surface Science. 2015;**357**:179-183

Semiconductor Processing. 2017;**64**:95-100

Materials Characterization. 2009;**60**:2-13

Magnetism and Magnetic Materials. 2012;**324**:797-801

status. Chemical Society Reviews. 2011;**40**(2011):3915-3940

Ni-implanted AlN. Surface Topography. 2014;**2**:035007

**Section 2**

**MeV Ion Beam Applications**

## **MeV Ion Beam Applications**

**Chapter 2**

**Provisional chapter**

at 300 K. For example,

. Irradiation of samples

, the origi-

**Ion-Nanoscale Matter Interactions**

**Ion-Nanoscale Matter Interactions**

DOI: 10.5772/intechopen.76862

Irradiation of spherical gold (Au) nanoparticles confined within a silica matrix with swift heavy ions induces their shaping into prolate nanorods along the beam direction. In this review, spherical colloidal Au nanoparticles with a diameter in the range of 15–30 nm (±3 nm) are irradiated at normal incidence with Ag ions with a kinetic energy in the

nally spherical nanoparticles of 15 nm diameter are shaped into prolate nanorods with a length of 40 nm and a width of 8 nm. An aspect ratio of the major to the minor axis of the nanorods of about 5.0 ± 0.4 at constant volume is achieved. Saturation of the varia-

containing 15 nm Au particles with 25 and 54 MeV Ag ions has shown further lengthening of the Au nanorods, increasing with the increasing ion energy. Similar ion-shaping behavior is reported for 30 nm Au particles under irradiation with 18, 25, and 54 MeV Ag ion energies, respectively. By systematically monitoring the experimental data, we put in evidence the existence of a threshold fluence of Au nanoparticle elongation. The value of the threshold fluence is found to depend on both the ion energy and nanoparticle size.

**Keywords:** ion beam, electronic stopping, Au nanoparticles, ion track, nanorods,

The use of ion beams as effective tools for changing the material properties has gained increasing interest during the past few decades. In particular, emphasis is given to ion implantation [1] and focused ion beam [2] processes which have received an enormous amount of attention

range of 18–54 MeV to fluences between 1013 and 1015 ions/cm<sup>2</sup>

tion of the aspect ratio is reached at a fluence of 8.7 × 1014 ions/cm<sup>2</sup>

under irradiation with 18 MeV Ag+4 ions to a fluence of 6.4 × 1014 ions/cm<sup>2</sup>

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.76862

Elmuez A. Dawi

Elmuez A. Dawi

**Abstract**

nanowires

**1. Introduction**

in semiconductor technology applications.

#### **Chapter 2 Provisional chapter**

#### **Ion-Nanoscale Matter Interactions Ion-Nanoscale Matter Interactions**

#### Elmuez A. Dawi Elmuez A. Dawi

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.76862

#### **Abstract**

Irradiation of spherical gold (Au) nanoparticles confined within a silica matrix with swift heavy ions induces their shaping into prolate nanorods along the beam direction. In this review, spherical colloidal Au nanoparticles with a diameter in the range of 15–30 nm (±3 nm) are irradiated at normal incidence with Ag ions with a kinetic energy in the range of 18–54 MeV to fluences between 1013 and 1015 ions/cm<sup>2</sup> at 300 K. For example, under irradiation with 18 MeV Ag+4 ions to a fluence of 6.4 × 1014 ions/cm<sup>2</sup> , the originally spherical nanoparticles of 15 nm diameter are shaped into prolate nanorods with a length of 40 nm and a width of 8 nm. An aspect ratio of the major to the minor axis of the nanorods of about 5.0 ± 0.4 at constant volume is achieved. Saturation of the variation of the aspect ratio is reached at a fluence of 8.7 × 1014 ions/cm<sup>2</sup> . Irradiation of samples containing 15 nm Au particles with 25 and 54 MeV Ag ions has shown further lengthening of the Au nanorods, increasing with the increasing ion energy. Similar ion-shaping behavior is reported for 30 nm Au particles under irradiation with 18, 25, and 54 MeV Ag ion energies, respectively. By systematically monitoring the experimental data, we put in evidence the existence of a threshold fluence of Au nanoparticle elongation. The value of the threshold fluence is found to depend on both the ion energy and nanoparticle size.

DOI: 10.5772/intechopen.76862

**Keywords:** ion beam, electronic stopping, Au nanoparticles, ion track, nanorods, nanowires

## **1. Introduction**

The use of ion beams as effective tools for changing the material properties has gained increasing interest during the past few decades. In particular, emphasis is given to ion implantation [1] and focused ion beam [2] processes which have received an enormous amount of attention in semiconductor technology applications.

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

When an ion penetrates a solid, it dissipates its kinetic energy in collisions with the target atoms. Ion implantation is performed in the energy regime where electronic stopping dominates the minimal sputtering mechanism. Implanted ion profile and the concentration of impurity atom are affected by sputtering. As the target material is being bombarded with energetic ions, some of the incident beam ions are implanted and retained in the target, while the surface that is exposed to the ion beam is simultaneously receding due to sputtering. Schematic diagram of the ion-solid interaction is illustrated in **Figure 1** (adopted from Nastasi et al. [3]). The basic mechanisms characterizing the interactions of ions with solids can be summarized as follows:

In the case of nuclear stopping, elastic collisions cause the ions to change their velocity, but the total kinetic energy of the colliding atoms remains constant. On the other hand, inelastic collisions involving electrons are not accompanied by large changes in the direction of the ion, and here several processes are possible: excitation and ionization of atoms with electron exchange in the colliding atoms. A typical evolution of the energy loss as a function of the ion kinetic energy is presented in **Figure 2** for a beam of xenon ions (Xe ions) in amorphous SiO<sup>2</sup>

From the figure, one can, for instance, infer that the electronic stopping power for an energy of 370 MeV is more than two orders of magnitude larger than the nuclear stopping power.

Heavy ions with ~MeV/a.m.u. kinetic energy predominantly lose their energy in a solid target material by electronic excitation and ionization of the target atoms. It is now well established that during irradiation with such ions, amorphous materials are subject to irreversible anisotropic changes of their specimen dimensions [4, 5]. Detailed description of the mechanism governing the anisotropic deformation is reported by the viscoelastic model. The latter presumes the deposition of energy by the incident ion into the electronic subsystem of the material. Through electron–phonon coupling, this energy is transformed in a cylindrical molten-like transient heating around the path of the particles. In a very short time interval (few femtoseconds), and as a result of the cylindrical molten expansion, shear stress relaxation induces freezing anisotropic stress as cooling of the heated regions is taking place. In this way,

**Figure 2.** Nuclear, electronic, and total energy loss versus the ion energy for typical ion energy of 370 MeV Xe in

. The figure is reproduced with permission from M. Toulemonde [8].

**1.1. Ion beam-induced deformation**

amorphous SiO<sup>2</sup>

**i.** Anisotropic plastic deformation of colloidal silica particles

.

17

Ion-Nanoscale Matter Interactions

http://dx.doi.org/10.5772/intechopen.76862

Taking into account the fact that most attention is paid to ion-induced structural changes of materials within nuclear and electronic energy loss regimes, we shall only discuss the two first mentioned mechanisms of the ion-matter interactions. A good approximation is the assumption that nuclear and electron energy losses are uncorrelated and can therefore be discussed separately and independently.

**Figure 1.** Schematic diagram of the ion solid interactions (adopted from Nastasi et al. [3]).

In the case of nuclear stopping, elastic collisions cause the ions to change their velocity, but the total kinetic energy of the colliding atoms remains constant. On the other hand, inelastic collisions involving electrons are not accompanied by large changes in the direction of the ion, and here several processes are possible: excitation and ionization of atoms with electron exchange in the colliding atoms. A typical evolution of the energy loss as a function of the ion kinetic energy is presented in **Figure 2** for a beam of xenon ions (Xe ions) in amorphous SiO<sup>2</sup> . From the figure, one can, for instance, infer that the electronic stopping power for an energy of 370 MeV is more than two orders of magnitude larger than the nuclear stopping power.

### **1.1. Ion beam-induced deformation**

When an ion penetrates a solid, it dissipates its kinetic energy in collisions with the target atoms. Ion implantation is performed in the energy regime where electronic stopping dominates the minimal sputtering mechanism. Implanted ion profile and the concentration of impurity atom are affected by sputtering. As the target material is being bombarded with energetic ions, some of the incident beam ions are implanted and retained in the target, while the surface that is exposed to the ion beam is simultaneously receding due to sputtering. Schematic diagram of the ion-solid interaction is illustrated in **Figure 1** (adopted from Nastasi et al. [3]). The basic mechanisms characterizing the interactions of ions with solids can be

**1.** Nuclear energy loss. This is the main mechanism of energy losses at low ion velocities (kinetic energy, corresponding to ~1 keV/a.m.u.). The bombarding particle transfers its energy to the nucleus of the target atom in elastic collisions, which causes the atoms to be

**2.** Electronic energy loss. This is the predominant mechanism of energy loss for fast ions (≥ 1 MeV/a.m.u.). In this regime the ions lose their kinetic energy by electronic excitation

**3.** Photon radiation. Stopping through photon generation becomes significant only at relativ-

**4.** Nuclear reactions. Nuclear reactions of the projectile ion and target atoms occur when the two collision partners have sufficient kinetic energy that the Coulomb barrier can be overcome

Taking into account the fact that most attention is paid to ion-induced structural changes of materials within nuclear and electronic energy loss regimes, we shall only discuss the two first mentioned mechanisms of the ion-matter interactions. A good approximation is the assumption that nuclear and electron energy losses are uncorrelated and can therefore be discussed

istic velocities (bremsstrahlung, transitional Vavilov-Cherenkov radiation).

**Figure 1.** Schematic diagram of the ion solid interactions (adopted from Nastasi et al. [3]).

summarized as follows:

16 Ion Beam Applications

displaced from their equilibrium positions.

and ionization of target atoms.

separately and independently.

**i.** Anisotropic plastic deformation of colloidal silica particles

Heavy ions with ~MeV/a.m.u. kinetic energy predominantly lose their energy in a solid target material by electronic excitation and ionization of the target atoms. It is now well established that during irradiation with such ions, amorphous materials are subject to irreversible anisotropic changes of their specimen dimensions [4, 5]. Detailed description of the mechanism governing the anisotropic deformation is reported by the viscoelastic model. The latter presumes the deposition of energy by the incident ion into the electronic subsystem of the material. Through electron–phonon coupling, this energy is transformed in a cylindrical molten-like transient heating around the path of the particles. In a very short time interval (few femtoseconds), and as a result of the cylindrical molten expansion, shear stress relaxation induces freezing anisotropic stress as cooling of the heated regions is taking place. In this way,

**Figure 2.** Nuclear, electronic, and total energy loss versus the ion energy for typical ion energy of 370 MeV Xe in amorphous SiO<sup>2</sup> . The figure is reproduced with permission from M. Toulemonde [8].

the deformation mechanism is governed by electronic energy loss and most efficiently with ions in the MeV/a.m.u. energy range. Extrapolation of experimental high-energy to lowerenergy data has suggested that the deformation is not expected to occur below a minimum irradiation energy of 1 MeV [6, 7]. The concept of the thermal spike is generally invoked to interpret the damage induced in amorphous materials such as metallic or silica glasses when they are traversed by ions with a kinetic energy in the electronic stopping regime.

**ii.** Anisotropic plastic deformation of embedded metal nanoparticles

Metal nanoparticles (NPs) are subject of large scientific and technological interest because of their specific properties which are different from those of the corresponding bulk material [9, 10]. When light impinges on (nano)-metal, the free conduction electron clouds respond collectively by oscillating in resonance, which excitation is known as a surface plasmon (SP). For a number of (noble) metals, the resonance behavior is noticeable in a single band in the visible range of the electromagnetic spectrum. One of the interesting aspects is the possibility to shift the surface plasmon resonance (SPR) peak of metal NPs into the infrared region by modifying their aspect ratio [11]. The SPR peak characteristics depend on the size, the shape, and the chemical environment of the metal NP; thus, modification of one of these parameters represents a way to control the optical properties of the material containing the NPs. In this respect, the ion beam-shaping technique is becoming a powerful tool to manipulate matter at the nanometer scale, allowing spherical dielectric particles to be transformed into prolate nanostructures, i.e., to elongate in direction perpendicular to the incident beam direction. Meanwhile, metal NPs embedded within a dielectric matrix are transformed into nanorods and/or nanowires that are aligned along the direction of the incident ion beam [12]. The latter is becoming an increasing scientific interest specially in tailoring the optical properties of plasmonic-active materials which could be widely used in applications within nanophotonics and nanoplasmonics [13].

with 15 and 30 nm diameter (a) and (b), respectively, and after immersion for 40 minutes into Au solution containing 15 and 30 nm diameter NPs, (c) and (d), respectively. These AFM images which were taken before sputter deposition of the second oxide layer show the uniformity of

A silicon dioxide layer with thickness of about 150 nm is reactively sputtered to cover the Au NPs. Subsequently, the layer structure is annealed at 900°C in an open furnace. To provide a good thermal contact during the irradiation treatment, the samples are mounted on a massive copper holder using conductive paste. For better understanding of ion energy and NP initial size dependence, irradiations with 18, 25, and 54 MeV Ag ions are performed on the first set of the samples. This first set is composed of three identically prepared NPs of 15 and 30 nm diameter each. The additional set of samples composed of the same NP size is prepared at higher NP areal density as to investigate the role of NP density within the resulting deformation characteristics of embedded NPs. The variation in Au NP areal density is established by variation of the immersion time of the samples into the Au-containing solution, between 5 and 40 minutes. The resulting density of the 15 and 30 nm Au NP samples obtained following the deposition scheme between 5 and 40 minutes is estimated in **Table 1**. The average interparticle distance is calculated based on a square array of particles. The ion beam is electrostatically scanned to homogeneously irradiate the entire sample area of 2 × 2 cm. Irradiations are per-

formed at room temperature (300 K) for fluences ranging from 1013 to 1015 ions/cm<sup>2</sup>

tandem accelerator. The values for the electronic stopping powers in SiO<sup>2</sup>

normal incidence. Beam currents are sufficiently stable during irradiations as measured on a

using a micro-Faraday cup. The beams are delivered by the Utrecht 6.5 MV EN

at the energies applied are deduced from the SRIM program

applying

and the projected

surface after immersion into Au solution for

Ion-Nanoscale Matter Interactions

19

http://dx.doi.org/10.5772/intechopen.76862

the Au NP distribution over the surface of the samples.

**Figure 3.** AFM images of 15 and 30 nm Au particles deposited on the SiO<sup>2</sup>

5 minutes, (a) and (b), respectively, and 40 minutes, (c) and (d), respectively.

spot of 1 mm<sup>2</sup>

range of the silver ions in SiO<sup>2</sup>

[17] and shown in **Table 2**.

## **2. Method**

Compared to conventional surface science techniques, such as gas-phase synthesis and deposition of NPs under ultrahigh-vacuum condition, the self-assembly of NPs by means of electrostatic coupling is a scientifically and economically interesting alternative [14]. In the following, charge-stabilized spherical colloidal gold NPs, which have been derivatized with (3-aminopropyl)triethoxysilane (APTES), are deposited on the surface of thermally grown silicon oxide substrates. The thickness of the thermal oxide amounts to 200 nm. Two sets of samples with the different NP size of 15 and 30 nm diameter are prepared. Dispersion in size is deduced from atomic force microscopy (AFM) technique. AFM analysis of the particle heights is measured and found to amount to about ±3 nm. Each set consists of a number of identically prepared samples for each NP size.

At present AFM is one of the important techniques for analysis of surface morphology [15, 16]. The size and shape of Au NPs have been inspected by a Nanoscope® IIIa tapping mode atomic force microscope (TM-AFM) operating in air. **Figure 3** shows AFM images of Au NPs, distributed on the sample surface after immersion for 5 minutes into a solution containing Au NPs

the deformation mechanism is governed by electronic energy loss and most efficiently with ions in the MeV/a.m.u. energy range. Extrapolation of experimental high-energy to lowerenergy data has suggested that the deformation is not expected to occur below a minimum irradiation energy of 1 MeV [6, 7]. The concept of the thermal spike is generally invoked to interpret the damage induced in amorphous materials such as metallic or silica glasses when

Metal nanoparticles (NPs) are subject of large scientific and technological interest because of their specific properties which are different from those of the corresponding bulk material [9, 10]. When light impinges on (nano)-metal, the free conduction electron clouds respond collectively by oscillating in resonance, which excitation is known as a surface plasmon (SP). For a number of (noble) metals, the resonance behavior is noticeable in a single band in the visible range of the electromagnetic spectrum. One of the interesting aspects is the possibility to shift the surface plasmon resonance (SPR) peak of metal NPs into the infrared region by modifying their aspect ratio [11]. The SPR peak characteristics depend on the size, the shape, and the chemical environment of the metal NP; thus, modification of one of these parameters represents a way to control the optical properties of the material containing the NPs. In this respect, the ion beam-shaping technique is becoming a powerful tool to manipulate matter at the nanometer scale, allowing spherical dielectric particles to be transformed into prolate nanostructures, i.e., to elongate in direction perpendicular to the incident beam direction. Meanwhile, metal NPs embedded within a dielectric matrix are transformed into nanorods and/or nanowires that are aligned along the direction of the incident ion beam [12]. The latter is becoming an increasing scientific interest specially in tailoring the optical properties of plasmonic-active materials which could be widely

Compared to conventional surface science techniques, such as gas-phase synthesis and deposition of NPs under ultrahigh-vacuum condition, the self-assembly of NPs by means of electrostatic coupling is a scientifically and economically interesting alternative [14]. In the following, charge-stabilized spherical colloidal gold NPs, which have been derivatized with (3-aminopropyl)triethoxysilane (APTES), are deposited on the surface of thermally grown silicon oxide substrates. The thickness of the thermal oxide amounts to 200 nm. Two sets of samples with the different NP size of 15 and 30 nm diameter are prepared. Dispersion in size is deduced from atomic force microscopy (AFM) technique. AFM analysis of the particle heights is measured and found to amount to about ±3 nm. Each set consists of a number of

At present AFM is one of the important techniques for analysis of surface morphology [15, 16]. The size and shape of Au NPs have been inspected by a Nanoscope® IIIa tapping mode atomic force microscope (TM-AFM) operating in air. **Figure 3** shows AFM images of Au NPs, distributed on the sample surface after immersion for 5 minutes into a solution containing Au NPs

they are traversed by ions with a kinetic energy in the electronic stopping regime.

**ii.** Anisotropic plastic deformation of embedded metal nanoparticles

used in applications within nanophotonics and nanoplasmonics [13].

identically prepared samples for each NP size.

**2. Method**

18 Ion Beam Applications

**Figure 3.** AFM images of 15 and 30 nm Au particles deposited on the SiO<sup>2</sup> surface after immersion into Au solution for 5 minutes, (a) and (b), respectively, and 40 minutes, (c) and (d), respectively.

with 15 and 30 nm diameter (a) and (b), respectively, and after immersion for 40 minutes into Au solution containing 15 and 30 nm diameter NPs, (c) and (d), respectively. These AFM images which were taken before sputter deposition of the second oxide layer show the uniformity of the Au NP distribution over the surface of the samples.

A silicon dioxide layer with thickness of about 150 nm is reactively sputtered to cover the Au NPs. Subsequently, the layer structure is annealed at 900°C in an open furnace. To provide a good thermal contact during the irradiation treatment, the samples are mounted on a massive copper holder using conductive paste. For better understanding of ion energy and NP initial size dependence, irradiations with 18, 25, and 54 MeV Ag ions are performed on the first set of the samples. This first set is composed of three identically prepared NPs of 15 and 30 nm diameter each. The additional set of samples composed of the same NP size is prepared at higher NP areal density as to investigate the role of NP density within the resulting deformation characteristics of embedded NPs. The variation in Au NP areal density is established by variation of the immersion time of the samples into the Au-containing solution, between 5 and 40 minutes. The resulting density of the 15 and 30 nm Au NP samples obtained following the deposition scheme between 5 and 40 minutes is estimated in **Table 1**. The average interparticle distance is calculated based on a square array of particles. The ion beam is electrostatically scanned to homogeneously irradiate the entire sample area of 2 × 2 cm. Irradiations are performed at room temperature (300 K) for fluences ranging from 1013 to 1015 ions/cm<sup>2</sup> applying normal incidence. Beam currents are sufficiently stable during irradiations as measured on a spot of 1 mm<sup>2</sup> using a micro-Faraday cup. The beams are delivered by the Utrecht 6.5 MV EN tandem accelerator. The values for the electronic stopping powers in SiO<sup>2</sup> and the projected range of the silver ions in SiO<sup>2</sup> at the energies applied are deduced from the SRIM program [17] and shown in **Table 2**.

**3. Results**

tions and/or areal densities (108

*3.1.1. Evolution of 15 nm Au NPs*

SiO<sup>2</sup>

respectively.

ions/cm<sup>2</sup>

(8.7 × 1014 ions/cm<sup>2</sup>

applying single ion energy of 54 MeV Ag+8 ions.

to the surface of a SiO<sup>2</sup>

Au NPs with average size of 15 and 30 nm diameter are prepared with different NP concentra-

heavy ion irradiation effects on these NPs. A selective range on incident ion energy of 18, 25, and 54 MeV Ag ions is applied. Influence of the ion energy, NP size, and areal density on the process of ion-induced elongation of spherical Au NPs will be discussed. For clarity of presentation, the "Results" section is divided into two subsections. The first subsection discusses the role played by embedded NP size and ion energy within the deformation characteristics at almost constant NP areal density and/or concentration. For that purpose, NP size range between 15 and 30 nm diameter is selected of which its samples are identically prepared and successively irradiated with ion beam energies in the range of 18–54 MeV Ag ions. In the second subsection, for the two NP sizes, the ion beam-induced deformation is investigated considering two extreme regions of NP areal density (low concentration and high concentration)

The first set consisting of three identically prepared samples, containing 15 nm Au NPs with

54 MeV Ag ions, respectively. **Figure 4a**–**c** shows the Au RBS peak as obtained from the 120° detector for several fluence values for the three energies. The relatively sharp peak of the

a plane at a depth of approximately 150 nm below the surface. RBS analysis in **Figure 4a**–**c** shows broadening in Au NP peak with increasing the irradiation fluence. The broadening in the Au RBS peak indicates that the depth distribution of the Au is penetrating into the hosting

From inspection of the data in both figures, two facts are deduced for irradiations of 15 nm Au

**i.** No elongation appears for fluences lower than ~5.0 × 1013 and 3.0 × 1013 ions/cm<sup>2</sup>

**ii.** The RBS peak width reaches saturation for fluences larger than ~6–8 × 1014 and 4.5 × 1014

The X-TEM micrographs in **Figure 6a**, **b** correspond to the highest 18 MeV irradiation fluence

diameter are all shaped into prolate nanorods with a length of ~40 nm and a width of ~8 nm, thus, with an aspect ratio of about 5. The volume of each nanorod corresponds approximately

). Clearly, under 18 MeV Ag+4 ions, the originally spherical NPs of 15 nm

 matrix. The latter indicates that the pristine Au NP is transformed into aligned nanorods parallel to the ion beam direction. The evolution of the FWHM with fluence from the 120° and

unirradiated regions corresponds to 15 nm particles which are embedded in a SiO<sup>2</sup>

matrix. In this section, we will report a detailed investigation of swift

) embedded within a single plane parallel

Ion-Nanoscale Matter Interactions

21

http://dx.doi.org/10.5772/intechopen.76862

, is irradiated with 18, 25, and

matrix in

,

–1010 particles/cm<sup>2</sup>

**3.1. Elongation as a function of the initial NP size and the ion beam energy**

an average areal density amounting to 1.7x1010 particles/cm<sup>2</sup>

170° detectors is shown in **Figures 5(a)** and **5(b)**, respectively.

NPs with 18 and 25 MeV Ag ions, as follows:

, respectively.

**Table 1.** NP concentration and the corresponding interparticle distance of Au NPs with average size of 15 and 30 nm diameter deposited on SiO<sup>2</sup> substrate by immersion of the substrate into colloidal Au-containing solution for time intervals of 5, 10, 20, 30, and 40 minutes.

These ranges are far beyond the thickness of the oxide layers containing the metal nanoparticles. Hence, the irradiation is only used to deposit energy into the SiO<sup>2</sup> -Au layers. The Au nanoparticle size and shape before and after irradiation are studied by using (tapping mode) atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM).

Analysis of the samples has been carried out by different techniques. Rutherford backscattering spectrometry (RBS) is used to measure the density of Au species as it penetrates into the SiO<sup>2</sup> matrix. With respect to the latter, RBS is regarded as a faster tool to bring information about Au NP depth distribution before and after irradiation with heavy ion beams. The depth distribution of the Au NPs is estimated from the corresponding full width at half maximum (FWHM) of the Au peak in the RBS spectra. It is worth mentioning that under swift heavy ion (SHI) irradiation, the vast majority of the Au species will not be confined to their NPs due to melting; therefore, the FWHM of the Au peak cannot bring qualitative estimation of the exact NP size. However, a qualitative trend of the NP elongation can be followed. RBS analysis was carried out applying an incident <sup>4</sup> He+ ion beam with energy of 2 MeV at normal incidence geometry. The backscattered ions were analyzed in situ using two detectors at angles of 120° and 170°, respectively. In the "Results" section, we will only discuss the data analysis obtained from one detector of our selection (120° detector), assuming that the data obtained from the 170° are essentially identical. After RBS analysis, samples containing the metal NPs are analyzed by transmission electron microscope (TEM) for cross-sectional imaging of the size and shape of Au NPs before and after irradiation. For that purpose, a 300 keV Philips/CM30 microscope is used. The micrographs obtained from X-TEM analysis are processed with a slow scanning camera applying digital micrograph program.

**Table 2.** Values for electronic (S<sup>e</sup> ) and nuclear (Sn) stopping power for SiO<sup>2</sup> and gold and projected range (Rp) obtained for the applied ion beams (18, 25, and 54 MeV Ag ions). All the values are obtained using the code SRIM 2008 [17].

## **3. Results**

These ranges are far beyond the thickness of the oxide layers containing the metal nanopar-

**Table 1.** NP concentration and the corresponding interparticle distance of Au NPs with average size of 15 and 30 nm

**Deposition time (±1 min) 5 minutes 10 minutes 20 minutes 30 minutes 40 minutes**

Interparticle distance (±10 nm) 200 115 85 76 50

Interparticle distance (±10 nm) — 333 208 188 176

2.5 × 10<sup>9</sup> 7.5 × 10<sup>9</sup> 1.4 × 1010 1.7 × 1010 4 × 1010

— 9 × 108 2.3 × 10<sup>9</sup> 2.8 × 10<sup>9</sup> 3.2 × 10<sup>9</sup>

substrate by immersion of the substrate into colloidal Au-containing solution for time

nanoparticle size and shape before and after irradiation are studied by using (tapping mode) atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS), and trans-

Analysis of the samples has been carried out by different techniques. Rutherford backscattering spectrometry (RBS) is used to measure the density of Au species as it penetrates into the SiO<sup>2</sup> matrix. With respect to the latter, RBS is regarded as a faster tool to bring information about Au NP depth distribution before and after irradiation with heavy ion beams. The depth distribution of the Au NPs is estimated from the corresponding full width at half maximum (FWHM) of the Au peak in the RBS spectra. It is worth mentioning that under swift heavy ion (SHI) irradiation, the vast majority of the Au species will not be confined to their NPs due to melting; therefore, the FWHM of the Au peak cannot bring qualitative estimation of the exact NP size. However, a qualitative trend of the NP elongation can be followed. RBS analysis was carried out applying an inci-

ion beam with energy of 2 MeV at normal incidence geometry. The backscattered ions

 **(Au) (keV/nm) Sn (Au) (keV/nm) Rp (μm)**

and gold and projected range (Rp) obtained for

were analyzed in situ using two detectors at angles of 120° and 170°, respectively. In the "Results" section, we will only discuss the data analysis obtained from one detector of our selection (120° detector), assuming that the data obtained from the 170° are essentially identical. After RBS analysis, samples containing the metal NPs are analyzed by transmission electron microscope (TEM) for cross-sectional imaging of the size and shape of Au NPs before and after irradiation. For that purpose, a 300 keV Philips/CM30 microscope is used. The micrographs obtained from X-TEM analysis are processed with a slow scanning camera applying digital micrograph program.

**) (keV/nm) Se**

18 MeV+4 5.4 0.23 11 0.9 5.8 25 MeV+5 6.7 0.18 14 0.7 6.9 54 MeV+8 9.7 0.10 24 0.4 10.3

) and nuclear (Sn) stopping power for SiO<sup>2</sup>

the applied ion beams (18, 25, and 54 MeV Ag ions). All the values are obtained using the code SRIM 2008 [17].

ticles. Hence, the irradiation is only used to deposit energy into the SiO<sup>2</sup>

mission electron microscopy (TEM).

15 nm Au NP concentration

30 nm Au NP concentration

diameter deposited on SiO<sup>2</sup>

) (±10%)

) (±10%)

intervals of 5, 10, 20, 30, and 40 minutes.

(particles/cm<sup>2</sup>

20 Ion Beam Applications

(particles/cm<sup>2</sup>

dent <sup>4</sup> He+

> **Se (SiO2**

**Table 2.** Values for electronic (S<sup>e</sup>

**) (keV/nm) Sn (SiO2**

Au NPs with average size of 15 and 30 nm diameter are prepared with different NP concentrations and/or areal densities (108 –1010 particles/cm<sup>2</sup> ) embedded within a single plane parallel to the surface of a SiO<sup>2</sup> matrix. In this section, we will report a detailed investigation of swift heavy ion irradiation effects on these NPs. A selective range on incident ion energy of 18, 25, and 54 MeV Ag ions is applied. Influence of the ion energy, NP size, and areal density on the process of ion-induced elongation of spherical Au NPs will be discussed. For clarity of presentation, the "Results" section is divided into two subsections. The first subsection discusses the role played by embedded NP size and ion energy within the deformation characteristics at almost constant NP areal density and/or concentration. For that purpose, NP size range between 15 and 30 nm diameter is selected of which its samples are identically prepared and successively irradiated with ion beam energies in the range of 18–54 MeV Ag ions. In the second subsection, for the two NP sizes, the ion beam-induced deformation is investigated considering two extreme regions of NP areal density (low concentration and high concentration) applying single ion energy of 54 MeV Ag+8 ions.

## **3.1. Elongation as a function of the initial NP size and the ion beam energy**

## *3.1.1. Evolution of 15 nm Au NPs*

The first set consisting of three identically prepared samples, containing 15 nm Au NPs with an average areal density amounting to 1.7x1010 particles/cm<sup>2</sup> , is irradiated with 18, 25, and 54 MeV Ag ions, respectively. **Figure 4a**–**c** shows the Au RBS peak as obtained from the 120° detector for several fluence values for the three energies. The relatively sharp peak of the unirradiated regions corresponds to 15 nm particles which are embedded in a SiO<sup>2</sup> matrix in a plane at a depth of approximately 150 nm below the surface. RBS analysis in **Figure 4a**–**c** shows broadening in Au NP peak with increasing the irradiation fluence. The broadening in the Au RBS peak indicates that the depth distribution of the Au is penetrating into the hosting SiO<sup>2</sup> matrix. The latter indicates that the pristine Au NP is transformed into aligned nanorods parallel to the ion beam direction. The evolution of the FWHM with fluence from the 120° and 170° detectors is shown in **Figures 5(a)** and **5(b)**, respectively.

From inspection of the data in both figures, two facts are deduced for irradiations of 15 nm Au NPs with 18 and 25 MeV Ag ions, as follows:

The X-TEM micrographs in **Figure 6a**, **b** correspond to the highest 18 MeV irradiation fluence (8.7 × 1014 ions/cm<sup>2</sup> ). Clearly, under 18 MeV Ag+4 ions, the originally spherical NPs of 15 nm diameter are all shaped into prolate nanorods with a length of ~40 nm and a width of ~8 nm, thus, with an aspect ratio of about 5. The volume of each nanorod corresponds approximately

**Figure 4.** Normalized RBS spectra of three identically prepared samples containing Au NPs with 15 nm diameter with an average areal density of 1.7x1010 particles/cm<sup>2</sup> after being irradiated with energies of 18 MeV Ag+4 ions, 25 MeV Ag+5 ions, and 54 MeV Ag+8 ions, (a), (b), and (c), respectively. The inset shows total normalized spectra for all samples. The Au surface channel is indicated. The scale is (a), and (b) is the same; however, for (c), the experimental condition is slightly different.

Strikingly, X-TEM micrographs corresponding to the irradiation with 54 MeV Ag+8 ions to

**Figure 6.** High-resolution X-TEM images of (i) 15 nm Au NPs under 18 MeV Ag+4 ions to a fluence of 8.7x1014 ions/cm<sup>2</sup>

in **Figure 6a**, **b**. These micrographs are given in **Figure 6c**, **d** showing aligned Au nanorods of approximately 40 nm length and ~8 nm width parallel to the ion beam direction. With

A second set of three identically prepared samples containing 30 nm Au NPs with a areal

ions. The series (a–c) in **Figure 7** represents the evolution of the Au RBS peak with irradiation fluence at these energies. **Figure 8** shows the change in FWHM with fluence derived from the RBS spectra for the three energies using the 120° detector. From the figure, two facts are deduced similar to the case for 15 nm Au NPs under irradiations with 18 and 25 MeV Ag ions,

**i.** Elongation threshold fluences are observed, amounting to about 7.0x1013 and 5.0x1013

**ii.** Saturation in FWHM of the Au RBS peak is reached at fluences 6.0x1014 and 5.0x1014 ions/

For irradiation with 54 MeV Ag+8 ions, the ion-shaping effect starts again without detectable threshold fluence. At the same time, no saturation is visible up to a fluence 2.0 × 1014 ions/cm<sup>2</sup>

broaden until its width becomes constant for fluences larger than 5.0 × 1014 ions/cm<sup>2</sup>

reveal almost similar nanorod morphology as those given

are irradiated with 18, 25, and 54 MeV Ag swift heavy

, the Au RBS peak continues to

(c) and (d). The direction of the ion

Ion-Nanoscale Matter Interactions

23

http://dx.doi.org/10.5772/intechopen.76862

.

.

a fluence of 1.0 × 1014 ions/cm<sup>2</sup>

beam is indicated by the black arrows.

*3.1.2. Evolution of 30 nm Au NPs*

, respectively.

, respectively.

density of about 2.8 × 10<sup>9</sup>

as follows:

ions/cm<sup>2</sup>

cm<sup>2</sup>

increasing the irradiation fluence above 1.0 × 1014 ions/cm<sup>2</sup>

(a) and (b). (ii) 15 nm NPs under 54 MeV Ag+8 ions to a fluence of 1.0 × 1014 ions/cm<sup>2</sup>

particles/cm<sup>2</sup>

**Figure 5.** The FWHM of the Au peak as function of irradiation fluence determined simultaneously for the 120° and 170° scattering angles, (a) and (b), respectively. The figures are for 15 nm Au NPs irradiated with 18 MeV Ag+4 ion energy (triangles and dot line), 25 MeV Ag+5 ion energy (circles and dash line), and 54 MeV Ag+8 ion energy (squares and solid line). A magnified view of the region identified by the black square and the black rectangle is included in the inset of figure (a) and (b), respectively.

to that of the pristine spherical NP (VNR~VNP). This indicates that the ion-shaping process for these irradiation conditions is an individual process, i.e., each NP deforms into a similar prolate nanorod.

The broadening of the Au RBS peak for the sample irradiated with 54 MeV Ag+8 ions is also represented in **Figure 5a**, **b**. At this energy the elongation of 15 nm Au particles starts without detectable threshold fluence in these measurements. After irradiation to a fluence of 1.0 × 1014 ions/cm<sup>2</sup> , the broadening of the Au RBS peak has already reached the value attained under irradiation with 18 MeV Ag+4 ions to the maximum fluence of 8.7 × 1014 ions/cm<sup>2</sup> . The latter observation confirms the influence of the ion energy on the elongation characteristics of Au NPs.

**Figure 6.** High-resolution X-TEM images of (i) 15 nm Au NPs under 18 MeV Ag+4 ions to a fluence of 8.7x1014 ions/cm<sup>2</sup> (a) and (b). (ii) 15 nm NPs under 54 MeV Ag+8 ions to a fluence of 1.0 × 1014 ions/cm<sup>2</sup> (c) and (d). The direction of the ion beam is indicated by the black arrows.

Strikingly, X-TEM micrographs corresponding to the irradiation with 54 MeV Ag+8 ions to a fluence of 1.0 × 1014 ions/cm<sup>2</sup> reveal almost similar nanorod morphology as those given in **Figure 6a**, **b**. These micrographs are given in **Figure 6c**, **d** showing aligned Au nanorods of approximately 40 nm length and ~8 nm width parallel to the ion beam direction. With increasing the irradiation fluence above 1.0 × 1014 ions/cm<sup>2</sup> , the Au RBS peak continues to broaden until its width becomes constant for fluences larger than 5.0 × 1014 ions/cm<sup>2</sup> .

## *3.1.2. Evolution of 30 nm Au NPs*

to that of the pristine spherical NP (VNR~VNP). This indicates that the ion-shaping process for these irradiation conditions is an individual process, i.e., each NP deforms into a similar

**Figure 5.** The FWHM of the Au peak as function of irradiation fluence determined simultaneously for the 120° and 170° scattering angles, (a) and (b), respectively. The figures are for 15 nm Au NPs irradiated with 18 MeV Ag+4 ion energy (triangles and dot line), 25 MeV Ag+5 ion energy (circles and dash line), and 54 MeV Ag+8 ion energy (squares and solid line). A magnified view of the region identified by the black square and the black rectangle is included in the inset of

**Figure 4.** Normalized RBS spectra of three identically prepared samples containing Au NPs with 15 nm diameter with an

and 54 MeV Ag+8 ions, (a), (b), and (c), respectively. The inset shows total normalized spectra for all samples. The Au surface channel is indicated. The scale is (a), and (b) is the same; however, for (c), the experimental condition is slightly different.

after being irradiated with energies of 18 MeV Ag+4 ions, 25 MeV Ag+5 ions,

The broadening of the Au RBS peak for the sample irradiated with 54 MeV Ag+8 ions is also represented in **Figure 5a**, **b**. At this energy the elongation of 15 nm Au particles starts without detectable threshold fluence in these measurements. After irradiation to a fluence of 1.0 × 1014

vation confirms the influence of the ion energy on the elongation characteristics of Au NPs.

diation with 18 MeV Ag+4 ions to the maximum fluence of 8.7 × 1014 ions/cm<sup>2</sup>

, the broadening of the Au RBS peak has already reached the value attained under irra-

. The latter obser-

prolate nanorod.

figure (a) and (b), respectively.

average areal density of 1.7x1010 particles/cm<sup>2</sup>

22 Ion Beam Applications

ions/cm<sup>2</sup>

A second set of three identically prepared samples containing 30 nm Au NPs with a areal density of about 2.8 × 10<sup>9</sup> particles/cm<sup>2</sup> are irradiated with 18, 25, and 54 MeV Ag swift heavy ions. The series (a–c) in **Figure 7** represents the evolution of the Au RBS peak with irradiation fluence at these energies. **Figure 8** shows the change in FWHM with fluence derived from the RBS spectra for the three energies using the 120° detector. From the figure, two facts are deduced similar to the case for 15 nm Au NPs under irradiations with 18 and 25 MeV Ag ions, as follows:

For irradiation with 54 MeV Ag+8 ions, the ion-shaping effect starts again without detectable threshold fluence. At the same time, no saturation is visible up to a fluence 2.0 × 1014 ions/cm<sup>2</sup> .

**Figure 7.** Normalized RBS spectra of 30 nm Au particles under (a) 18 MeV Ag+4 ions, (b) 25 MeV Ag+5 ions, and (c) 54 MeV Ag+8 ions for samples prepared with an average areal density of 2.8 × 10<sup>9</sup> particles/cm<sup>2</sup> .

AFM analysis in **Figure 3** points to a good uniformity of Au NP distribution over the surface and the absence of agglomeration, i.e., clustering of individual NPs. This allows us to investigate the role of interparticle distance on the ion-shaping mechanism. Thus, in the following subsection, we will focus on the elongation phenomenon by varying the initial areal density of the Au NPs.

(a–c) in **Figure 9** show the 15 nm Au RBS peak for various fluences for NP at areal density

**Figure 9.** The Au RBS peak of 15 Au NPs for various irradiation fluences of 54 MeV Ag+8 ions for different areal densities

of the FWHM of the RBS Au peak as a function of the fluence, for various values of the areal density. From the inspection of the figure, two regions clearly appear as follows: (i) For low irradiation fluences, the relative broadening of the RBS peak is almost the same for all samples irrespective of their areal density. We define this region as A. (ii) Above a critical fluence of

the NP areal density. This region is denoted as region B. Apparently, all the curves tend to evolve toward a saturation value. The larger the initial NP areal density, the larger the satura-

We presume that in region A, Au NPs elongate into nanorods conserving their original volume (VNR~VNP). This is confirmed by X-TEM analysis as is shown in **Figure 11a**–**d**. To understand correlations between NP areal density and/or concentration and the broadening within the Au RBS peak observed in region B in **Figure 10**, we have selected two X-TEM micrographs of extreme NP densities (lower/higher) for comparison. As for the lowest NP density of 2.5 × 10<sup>9</sup>

with major to minor axes of 100.8 nm. Calculation of the corresponding volume of these nanorods indicates that the volume for each nanorod is about twice the volume of the original pristine NP (VNR~2VNP). Then, we consider the TEM micrographs corresponding to the high-

micrographs are given in **Figure 11c**–**e** and show long nanowires with their major axis varying from 150 to 180 nm and minor axis of 8 nm. It is obvious that these wires are not the result of the deformation of a single particle because their Au content exceeds that of the initial NPs by at least a factor of 5 to 6, i.e., VNR~ (5–6) VNP. We attribute that multiple Au NPs must have contributed to the growth of such nanowires. Seemingly, under swift heavy ion irradiation, some NPs deliver their species by disintegration, and through lateral transport, the disintegrated particles contribute to the growth of other particles. In this way, further lengthened nanostructures will appear in account of shorter ones. The latter hypothesis has been confirmed by X-TEM analysis where we observed smaller aligned particles, likely resulting from the fragmentation of some

, TEM micrographs in **Figure 11a**, **b** which correspond to irradiation fluence of

is shown. The X-TEM micrograph in this figure shows aligned Au nanorods

) at a fluence of 5.0 × 1014 ions/cm<sup>2</sup>

, respectively. **Figure 10** shows the evolution

Ion-Nanoscale Matter Interactions

25

http://dx.doi.org/10.5772/intechopen.76862

, (a), (b), and (c), respectively. Normalized RBS spectra are presented in

(see **Figure 11**). These

, the broadening of the RBS peak becomes significantly a function of

, 1.4 × 1010, and 4 × 1010 particles/cm<sup>2</sup>

, 1.4 × 1010, and 4 × 1010 particles/cm<sup>2</sup>

of 2.5 × 10<sup>9</sup>

of 2.5 × 10<sup>9</sup>

the inset of plot (c).

particles/cm<sup>2</sup>

8.0x1014 ions/cm<sup>2</sup>

about 1–2 × 1014 ions/cm<sup>2</sup>

tion value of the FWHM appears to be.

est areal density (4 × 1010 particles/cm<sup>2</sup>

#### **3.2. Elongation as a function of the initial NP size and initial NP concentration**

#### *3.2.1. Evolution of 15 nm Au NPs*

Samples containing spherical Au NPs with diameter of 15 nm prepared with areal density between 0.25 and 4 × 1010 particles/cm<sup>2</sup> were irradiated with 54 MeV Ag+8 ions. The series

**Figure 8.** The relative change of Au peak width determined for the 120° scattering angle as a function of fluence for 30 nm Au particles under irradiation with 18 MeV Ag+4 ions (triangles and dot line), 25 MeV Ag+5 ions (circles and dash line), and 54 MeV Ag+8 ions (squares and solid line).

**Figure 9.** The Au RBS peak of 15 Au NPs for various irradiation fluences of 54 MeV Ag+8 ions for different areal densities of 2.5 × 10<sup>9</sup> , 1.4 × 1010, and 4 × 1010 particles/cm<sup>2</sup> , (a), (b), and (c), respectively. Normalized RBS spectra are presented in the inset of plot (c).

(a–c) in **Figure 9** show the 15 nm Au RBS peak for various fluences for NP at areal density of 2.5 × 10<sup>9</sup> , 1.4 × 1010, and 4 × 1010 particles/cm<sup>2</sup> , respectively. **Figure 10** shows the evolution of the FWHM of the RBS Au peak as a function of the fluence, for various values of the areal density. From the inspection of the figure, two regions clearly appear as follows: (i) For low irradiation fluences, the relative broadening of the RBS peak is almost the same for all samples irrespective of their areal density. We define this region as A. (ii) Above a critical fluence of about 1–2 × 1014 ions/cm<sup>2</sup> , the broadening of the RBS peak becomes significantly a function of the NP areal density. This region is denoted as region B. Apparently, all the curves tend to evolve toward a saturation value. The larger the initial NP areal density, the larger the saturation value of the FWHM appears to be.

We presume that in region A, Au NPs elongate into nanorods conserving their original volume (VNR~VNP). This is confirmed by X-TEM analysis as is shown in **Figure 11a**–**d**. To understand correlations between NP areal density and/or concentration and the broadening within the Au RBS peak observed in region B in **Figure 10**, we have selected two X-TEM micrographs of extreme NP densities (lower/higher) for comparison. As for the lowest NP density of 2.5 × 10<sup>9</sup> particles/cm<sup>2</sup> , TEM micrographs in **Figure 11a**, **b** which correspond to irradiation fluence of 8.0x1014 ions/cm<sup>2</sup> is shown. The X-TEM micrograph in this figure shows aligned Au nanorods with major to minor axes of 100.8 nm. Calculation of the corresponding volume of these nanorods indicates that the volume for each nanorod is about twice the volume of the original pristine NP (VNR~2VNP). Then, we consider the TEM micrographs corresponding to the highest areal density (4 × 1010 particles/cm<sup>2</sup> ) at a fluence of 5.0 × 1014 ions/cm<sup>2</sup> (see **Figure 11**). These micrographs are given in **Figure 11c**–**e** and show long nanowires with their major axis varying from 150 to 180 nm and minor axis of 8 nm. It is obvious that these wires are not the result of the deformation of a single particle because their Au content exceeds that of the initial NPs by at least a factor of 5 to 6, i.e., VNR~ (5–6) VNP. We attribute that multiple Au NPs must have contributed to the growth of such nanowires. Seemingly, under swift heavy ion irradiation, some NPs deliver their species by disintegration, and through lateral transport, the disintegrated particles contribute to the growth of other particles. In this way, further lengthened nanostructures will appear in account of shorter ones. The latter hypothesis has been confirmed by X-TEM analysis where we observed smaller aligned particles, likely resulting from the fragmentation of some

**Figure 8.** The relative change of Au peak width determined for the 120° scattering angle as a function of fluence for 30 nm Au particles under irradiation with 18 MeV Ag+4 ions (triangles and dot line), 25 MeV Ag+5 ions (circles and dash line),

AFM analysis in **Figure 3** points to a good uniformity of Au NP distribution over the surface and the absence of agglomeration, i.e., clustering of individual NPs. This allows us to investigate the role of interparticle distance on the ion-shaping mechanism. Thus, in the following subsection, we will focus on the elongation phenomenon by varying the initial areal density of the Au NPs.

**Figure 7.** Normalized RBS spectra of 30 nm Au particles under (a) 18 MeV Ag+4 ions, (b) 25 MeV Ag+5 ions, and (c) 54 MeV

Samples containing spherical Au NPs with diameter of 15 nm prepared with areal density

were irradiated with 54 MeV Ag+8 ions. The series

particles/cm<sup>2</sup>

.

**3.2. Elongation as a function of the initial NP size and initial NP concentration**

and 54 MeV Ag+8 ions (squares and solid line).

*3.2.1. Evolution of 15 nm Au NPs*

24 Ion Beam Applications

between 0.25 and 4 × 1010 particles/cm<sup>2</sup>

Ag+8 ions for samples prepared with an average areal density of 2.8 × 10<sup>9</sup>

and above the critical fluence of 1.0 × 1014 ions/cm<sup>2</sup>

limited by a too large distance between the Au NPs.

with 54 MeV Ag+8 ions to a fluence of 5.0 x 1014 ions/cm<sup>2</sup>

at an areal density of approximately 9.0 x 108

particles/cm<sup>2</sup>

areal density of ~5.0 × 10<sup>9</sup>

and 3.2 × 10<sup>9</sup>

ions/cm<sup>2</sup>

of 9.0 × 108

the inset of plot (c).

, 2.8 × 10<sup>9</sup>

, and 3.2 × 10<sup>9</sup>

particles/cm<sup>2</sup>

*3.2.2. Evolution of 30 nm Au NPs*

particles/cm<sup>2</sup>

continue to grow by accumulation of atoms and/or fragments from the disintegrating particles. The latter is assumed to occur by means of a process that is well known as Ostwald ripening. Interestingly, in some regions of TEM micrographs, tiny satellite particles surrounding shorter particles were seen (inset of **Figure 11c**). These satellite particles were not visible before irradiation. It is clear that the relative increase in Au peak width of the lowest areal density sample has already attained its maximum value just above the critical fluence. This might imply that there exists a threshold areal density for nanowire formation for 15 nm diameter Au particles, at an

an interparticle distance of about 150 nm. Presumably, the mass transport process is effectively

Au NPs having an average diameter of about 30 nm and areal density ranging between 0.9

Again, we report the existence of two separated regions as in **Figure 10**. At lower irradiation fluences, the Au NP broadening evolves the NP size (region A). However, for fluences larger

in Au NPs in region B evolves the NP areal density. As can be seen in **Figure 14a**, **b**, X-TEM micrographs show Au nanowires of a length of about 150~200 nm and a width of 8 nm align-

figure, we deduce a threshold interparticle distance near 250 nm for nanowire formation, i.e.,

**Figure 12.** The Au RBS peak of 30 Au NPs for various irradiation fluences of 54 MeV Ag+8 ions for different areal densities

particles/cm<sup>2</sup>

.

, (a), (b), and (c), respectively. Normalized RBS spectra are presented in

each NP areal density are shown in **Figure 12a**–**c** and **Figure 13**, respectively.

than a certain value (estimated for this NP size of about 1.0 x 1014 ions/cm<sup>2</sup>

ing as a result from irradiation of the 30 nm Au NPs with areal density of 3.2 × 10<sup>9</sup>

. The Au RBS peaks and the evolution of the FWHM of Au peak with the fluence for

, Au NPs start to disintegrate, while others

http://dx.doi.org/10.5772/intechopen.76862

Ion-Nanoscale Matter Interactions

27

), the broadening

particles/cm<sup>2</sup>

(see **Figure 3.5**). From the data in this

, under 54 MeV Ag+8 ion irradiation. This corresponds to

were irradiated with 54 MeV Ag+8 ions up to a fluence of 5.0 × 1014

**Figure 10.** The FWHM of Au RBS peak obtained from the 120° detector as a function of 54 MeV Ag+8 irradiation fluence for different areal densities of 15 nm Au particles.

**Figure 11.** HR-XTEM images of (i) 15 nm Au particles with initial areal density of about 2.5 × 10<sup>9</sup> particles/cm<sup>2</sup> after irradiation with 54 MeV Ag+8 ions to a fluence of 8.1 × 1014 ions/cm<sup>2</sup> , (a) and (b), respectively. (ii) 15 nm Au particles with an initial areal density of 4.0 × 1010 particles/cm<sup>2</sup> irradiated with 54 MeV Ag+8 ions to a fluence of 5.0 × 1014 ions/cm<sup>2</sup> , (c), (d), and (e), respectively. The direction of the ion beam is indicated by the black arrows.

ion-deformed nanorods or nanowires. It emerges that the variation of NP areal density, and the concomitant variation of the interparticle distance, results in a strong variation in the shaping characteristics of the spherical Au NPs. For the areal density larger than 2.5 × 10<sup>9</sup> particles/cm<sup>2</sup>

and above the critical fluence of 1.0 × 1014 ions/cm<sup>2</sup> , Au NPs start to disintegrate, while others continue to grow by accumulation of atoms and/or fragments from the disintegrating particles. The latter is assumed to occur by means of a process that is well known as Ostwald ripening. Interestingly, in some regions of TEM micrographs, tiny satellite particles surrounding shorter particles were seen (inset of **Figure 11c**). These satellite particles were not visible before irradiation. It is clear that the relative increase in Au peak width of the lowest areal density sample has already attained its maximum value just above the critical fluence. This might imply that there exists a threshold areal density for nanowire formation for 15 nm diameter Au particles, at an areal density of ~5.0 × 10<sup>9</sup> particles/cm<sup>2</sup> , under 54 MeV Ag+8 ion irradiation. This corresponds to an interparticle distance of about 150 nm. Presumably, the mass transport process is effectively limited by a too large distance between the Au NPs.

## *3.2.2. Evolution of 30 nm Au NPs*

ion-deformed nanorods or nanowires. It emerges that the variation of NP areal density, and the concomitant variation of the interparticle distance, results in a strong variation in the shaping

**Figure 10.** The FWHM of Au RBS peak obtained from the 120° detector as a function of 54 MeV Ag+8 irradiation fluence

particles/cm<sup>2</sup>

particles/cm<sup>2</sup>

, (a) and (b), respectively. (ii) 15 nm Au particles with

irradiated with 54 MeV Ag+8 ions to a fluence of 5.0 × 1014 ions/cm<sup>2</sup>

after

, (c),

characteristics of the spherical Au NPs. For the areal density larger than 2.5 × 10<sup>9</sup>

**Figure 11.** HR-XTEM images of (i) 15 nm Au particles with initial areal density of about 2.5 × 10<sup>9</sup>

(d), and (e), respectively. The direction of the ion beam is indicated by the black arrows.

irradiation with 54 MeV Ag+8 ions to a fluence of 8.1 × 1014 ions/cm<sup>2</sup>

an initial areal density of 4.0 × 1010 particles/cm<sup>2</sup>

for different areal densities of 15 nm Au particles.

26 Ion Beam Applications

Au NPs having an average diameter of about 30 nm and areal density ranging between 0.9 and 3.2 × 10<sup>9</sup> particles/cm<sup>2</sup> were irradiated with 54 MeV Ag+8 ions up to a fluence of 5.0 × 1014 ions/cm<sup>2</sup> . The Au RBS peaks and the evolution of the FWHM of Au peak with the fluence for each NP areal density are shown in **Figure 12a**–**c** and **Figure 13**, respectively.

Again, we report the existence of two separated regions as in **Figure 10**. At lower irradiation fluences, the Au NP broadening evolves the NP size (region A). However, for fluences larger than a certain value (estimated for this NP size of about 1.0 x 1014 ions/cm<sup>2</sup> ), the broadening in Au NPs in region B evolves the NP areal density. As can be seen in **Figure 14a**, **b**, X-TEM micrographs show Au nanowires of a length of about 150~200 nm and a width of 8 nm aligning as a result from irradiation of the 30 nm Au NPs with areal density of 3.2 × 10<sup>9</sup> particles/cm<sup>2</sup> with 54 MeV Ag+8 ions to a fluence of 5.0 x 1014 ions/cm<sup>2</sup> (see **Figure 3.5**). From the data in this figure, we deduce a threshold interparticle distance near 250 nm for nanowire formation, i.e., at an areal density of approximately 9.0 x 108 particles/cm<sup>2</sup> .

**Figure 12.** The Au RBS peak of 30 Au NPs for various irradiation fluences of 54 MeV Ag+8 ions for different areal densities of 9.0 × 108 , 2.8 × 10<sup>9</sup> , and 3.2 × 10<sup>9</sup> particles/cm<sup>2</sup> , (a), (b), and (c), respectively. Normalized RBS spectra are presented in the inset of plot (c).

for 15–80 nm Au particles is estimated in **Table 3**. The value of Φ<sup>c</sup>

incident ion energy. These mechanisms are listed as followed:

**ii.** The compaction of the hosting silica matrix under irradiation.

**i.** Preparation methodology of the samples.

unknown. Following the process, our SiO<sup>2</sup>

that a certain compaction of the SiO<sup>2</sup>

tion process is activated.

es, the SiO<sup>2</sup>

18 MeV Ag+4 25 MeV Ag+5

18 MeV Ag+4 25 MeV Ag+5

top of a thermally grown SiO<sup>2</sup>

substrate.

ary layer of SiO<sup>2</sup>

stopping power and increases with the NP diameter. However, as suggested by Klaumünzer [18, 19] and successively experimentally shown by Penninkhof et al. [20, 21], irradiationinduced NP elongation is a complicated issue where both the matrix and the characteristics of the confined NPs play an active role. Here, we put forward three possible mechanisms that could be the origin of the existence of a threshold fluence and its variation with NP size and

**iii.** Occurrence of the irradiation-induced stresses within the silica matrix constrained by a

**iv.** Following the process at which our samples are prepared, Au NPs are first assembled on

tion of the active region of the samples indicates that Au NPs are embedded in a single plane 200 nm far from the surface of the sample. Chemically, gold is known to have a fairly poor wetting affinity with the SiO2. Consequently, the mechanism of how precisely the oxide layer is formed around the Au NP during the deposition process is basically

mobility growth mode [22] and relatively low ion bombardment energy [23]. Within this sputtering scheme, most likely voids will form near the lower half of the NP in the growing oxide. The latter is attributed due to shadowing effects. On the other hand, during X-TEM analysis, none of the aforementioned voids were imaged. Therefore, it is plausible

**v.** It has been mentioned in literature that under irradiation with swift heavy ions at low fluenc-

material into smaller compact ring volume leads to densification of the silica matrix [28, 29]. For swift heavy ion irradiation, within each individual cylindrical ion track, the virgin material density is irreversibly modified. Subsequent ion impact within the same region does not produce any further density changes [24]. In this view, the fluence required to achieve

sotropic growth dominates the compaction phase [24–27]. Rearrangement of the SiO<sup>2</sup>

**Ion energy Nanoparticle size (nm) Threshold fluence (ions/cm<sup>2</sup>**

15 5 × 1013

30 7 × 1013

**Table 3.** The threshold fluence for elongation as a function of ion energy and NP size for 15–80 nm Au particles.

matrix exhibits a compaction of about 3%. At higher irradiation fluences, an ani-

3 × 1013

5 × 1013

film and subsequently confined by sputtering of a second-

top film is grown at zone 1 at the low adatom

**)**

ringlike

surrounding the NP is required before the deforma-

that is reactively sputtered on top of the first layer. The final configura-

on both ion energy and pristine NP size. In particular, Φ<sup>c</sup>

has been observed to depend

Ion-Nanoscale Matter Interactions

29

decreases with increasing electronic

http://dx.doi.org/10.5772/intechopen.76862

**Figure 13.** The FWHM of Au RBS peak obtained from only the 120° detector as a function of 54 MeV Ag+8 irradiation fluence for different areal densities of 30 nm Au particles.

**Figure 14.** HR-XTEM images of 30 nm Au particles with initial areal density of 3.2 × 10<sup>9</sup> particles/cm<sup>2</sup> irradiated with 54 MeV Ag+8 ions to a fluence of 5.0 × 1014 ions/cm<sup>2</sup> , (a) and (b), respectively. The direction of the ion beam is indicated by the black arrows.

## **4. Discussion**

As pointed out in the experimental section, the projected ranges of the ions at the applied energies are far beyond the location of the spherical Au NPs. Thus, the elongation of such metal NPs must be a result of the ion passage through the SiO<sup>2</sup> -Au-containing layer.

Systematic investigations of the deformation of NPs in response to swift heavy ion (SHI) irradiation have allowed us to evidence experimentally the existence of a threshold fluence for elongation, Φ<sup>c</sup> . The threshold fluence for elongation as a function of ion energy and NP size for 15–80 nm Au particles is estimated in **Table 3**. The value of Φ<sup>c</sup> has been observed to depend on both ion energy and pristine NP size. In particular, Φ<sup>c</sup> decreases with increasing electronic stopping power and increases with the NP diameter. However, as suggested by Klaumünzer [18, 19] and successively experimentally shown by Penninkhof et al. [20, 21], irradiationinduced NP elongation is a complicated issue where both the matrix and the characteristics of the confined NPs play an active role. Here, we put forward three possible mechanisms that could be the origin of the existence of a threshold fluence and its variation with NP size and incident ion energy. These mechanisms are listed as followed:

**i.** Preparation methodology of the samples.

**Figure 13.** The FWHM of Au RBS peak obtained from only the 120° detector as a function of 54 MeV Ag+8 irradiation

As pointed out in the experimental section, the projected ranges of the ions at the applied energies are far beyond the location of the spherical Au NPs. Thus, the elongation of such

Systematic investigations of the deformation of NPs in response to swift heavy ion (SHI) irradiation have allowed us to evidence experimentally the existence of a threshold fluence for

. The threshold fluence for elongation as a function of ion energy and NP size

particles/cm<sup>2</sup>

, (a) and (b), respectively. The direction of the ion beam is indicated

irradiated with

**Figure 14.** HR-XTEM images of 30 nm Au particles with initial areal density of 3.2 × 10<sup>9</sup>

metal NPs must be a result of the ion passage through the SiO<sup>2</sup>

fluence for different areal densities of 30 nm Au particles.

54 MeV Ag+8 ions to a fluence of 5.0 × 1014 ions/cm<sup>2</sup>

by the black arrows.

28 Ion Beam Applications

**4. Discussion**

elongation, Φ<sup>c</sup>

**Table 3.** The threshold fluence for elongation as a function of ion energy and NP size for 15–80 nm Au particles.

the compaction corresponds slightly to a compromise where all incident neighboring tracks exhibit mutual overlap in such way that the perturbed area covers the overall sample surface.

the temperatures of both the metallic NP and the surrounding dielectric matrix exceed their individual melting temperatures [18, 19]. In literature, it has been argued that the melting of metallic NPs with diameters in the range of nearly similar range to our NPs of the current study (6 and 20 nm) cannot be invoked with energy deposition corresponding to the electronic stopping powers in the current work [35]. Particles with relatively larger diameters are not expected to completely melt and virtually are not observed to deform under SHI irradiation, [18, 35, 36]. Awazu et al. [35] report that Au NPs with diameter of about 50 nm are not subject to deform under irradiation with 110 MeV Br ions to a fluence of about 1.0 × 1014 ions/cm<sup>2</sup>

this class of NP size, it is conceivable that a minimum compressive stress is needed to activate the NP deformation. On the other hand, it is necessary to mention that the threshold fluence cannot be directly regarded to the individual track-generated stress [37–39]. This is because the deformation threshold would be only dependable on the electronic stopping. Consequently, macroscopic stress should be invoked to clarify the observations. In this sense, direct correlation between minimum compressive stress and NP size could be established. The larger NP size requires larger (minimum) compressive stress to activate the NP elongation process leading to larger fluence necessary to reach it. The latter hypothesis accounts quiet well for our results for the deformation dependence on initial NP size, ion energy, and irradiation fluence. Furthermore, the variation of the embedded NP areal density has led to identification of two distinct fluence regimes for the NP elongation under swift heavy ion irradiations as follows:

**i.** For low irradiation fluences, Au NPs deform into ion beam-aligned nanorods. This morphology transformation occurs under volume conservation. In other words, the ion-shaping mechanism is an individual mechanism, where each pristine NP deforms into a single oblate nanorod. As this behavior is observed for all values of the NP areal density, in this first stage which is represented by the region A, the ion-shaping process can be seen as an *individual*

**ii.** For irradiation fluences above—somewhat critical threshold—of 1.0 x1014 ions/cm<sup>2</sup>

analysis indicates that the deformation rate is sensitive to the initial NP areal density. With increasing the NP areal density, the deformation rate increases. In this deformation's secondary stage, high-resolution TEM images show long Au nanowires aligned in direction of the ion beam accompanied by strong signs of Au disintegration and/or fragmentation. As the volume of the longer nanowires visualized is about five to six times the volume of the originally spherical NP, the NP elongation process in this fluencedependent region necessitates the contribution of several individual nanostructures. Within this fluence region, the elongation process might be identified in terms of a *collective process* where some of already-deformed NPs, or even some of the aligned nanowires, dissolve under the irradiation, while other nanowires continue to grow by integration of the atoms from the dissolving particles. The mechanism behind the driving force identifies which nanowire should dissolve and which nanowire should grow remain unknown. Consequently, there is a need for more detailed experimental and theoretical approach

The mechanism governing the growth of Au nanowires most likely involves the diffusion through the silica matrix of the gold solute from the dissolved/fragmented nanoparticles toward the growing ones. The task to identify the physical origin of the driving force for preferred Au diffusion from shorter Au nanorods to longer ones, which causes a kind of Ostwald ripening, is difficult.

*process* as far as the nanoparticles are concerned.

to verify it.

. For

31

Ion-Nanoscale Matter Interactions

http://dx.doi.org/10.5772/intechopen.76862

, RBS

**vi.** As mentioned in our experimental part, our grown silica film is not free standing films but constrained by underneath silicon substrate. The stress state of a constrained silica film as an effect of the ion irradiation has been intensively studied in literature [25–27]. Two extremely opposite stress situations depending on the irradiation fluence have been reported as follows: (1) under irradiation at low ion fluences, the initially compressive stress turns into a tensile stress. The latter, which is related to the mechanism of compaction, leads to the structure to a higher equilibrium density state. The maximum value for this equilibrium is reached at the end of the matrix densification for fluences up to few 1013 ions/cm<sup>2</sup> . (2) Under irradiation with fluences larger than 1014 ions/cm<sup>2</sup> , anisotropic material deformation becomes quiet prominent in the further evolution of the system. The latter effect is associated with the tensile stress reduction and the buildup of a compressive stress for the constrained film.

Considering mechanisms (i) and (ii), we presume that the NP elongation is limited to the accomplishment of the structural transformation of the silica matrix. With the latter in mind, we try to correlate the threshold deformation evolution with the energy of the incident ions. As the end of SiO<sup>2</sup> matrix compaction implies the situation whereas the sample surface becomes entirely covered by the mutually overlapping ion tracks, it is conceivable that the resulting deformation threshold depends on the incident ion track diameter. In that sense, the larger the track radius is, the lower the deformation threshold fluence will be. In literature, a number of experimental and theoretical publications have already reported on the ion track cross sections in SiO<sup>2</sup> matrix [30–33]. In these publications, the track size is calculated from the thermal spike model and already found to correspond to the region that melted in the wake of the passing heavy projectile [34]. In our current results, the applied ion energies of 18, 25, and 54 MeV Ag, the corresponding electronic stopping powers in SiO<sup>2</sup> amount to 5.4, 6.7 and 9.7 keV/nm). The corresponding track diameters for these energies in the silica are approximately 3, 4, and ~5 nm, respectively. The calculated corresponding complete overlap of the ion tracks at the surface of the sample is found at fluences of 2.0 × 1013, 1.0 × 1013, 0.7 × 1013, and 0.5 × 1013 ions/cm<sup>2</sup> , respectively.

Putting on mind that (i) the swift heavy ion irradiation follows random statistics and that (ii) the compaction fluence for a silica matrix containing partially wetted metallic NP can be different from that of pure silica film, our calculations account pretty well for the reported reduction of the deformation threshold when the incident ion energy is increased.