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IBM eyes molecule 'anatomy' for future computers



Pentacene molecule
By using an atomically sharp metal tip terminated with a carbon monoxide molecule, IBM scientists were able to obtain an image of the inner structure of the molecule. The colored surface represents experimental data. The model below shows the position of the atoms within the molecule. IBM

Scientists In Zurich, Switzerland, have, for the first time, imaged the "anatomy," or chemical structure, of an individual molecule with "unprecedented" resolution, using noncontact atomic force microscopy (AFM), IBM said Thursday. Resolving individual atoms within a molecule has been a long-standing goal of surface microscopy, according to the computer company, which has a research and development program dating back to 1945.

This research will be essential for building computing elements at the atomic scale that are vastly smaller, faster and more energy-efficient than today's processors and memory devices, IBM said.

The research is reported in the August 28 issue of Science magazine.

Though in recent years progress has been made in research of nanostructures on the atomic scale with AFM, imaging the chemical structure of an entire molecule has never been achieved with atomic resolution, according to IBM.

The atomic force microscopy was done in an ultrahigh vacuum and at very low temperatures (5 Kelvin equals minus 268 degrees Centigrade or minus 451 Fahrenheit) to image the chemical structure of individual pentacene molecules. Pentacene has a crystal structure that gives it properties as an organic semiconductor.

Scientists were able "to look through the electron cloud and see the atomic backbone of an individual molecule for the first time." This is roughly analogous to X-rays that pass through soft tissue to enable clear images of bones, IBM said.

The Science magazine article follows another piece published two months ago in the June 12 issue of the magazine covering the "determination of atomic charge states." The results discussed in both of these articles will "open new possibilities for investigating how charge propagates through molecules or molecular networks," IBM said.

Understanding the charge distribution may lead to building computing elements at the atomic scale. This is the Holy Grail of semiconductor research and development. As circuit geometries get infinitesimally smaller, it becomes prohibitively challenging to make circuits with geometries below 10 nanometers, or even 20 nanometers."

"It is accepted that in the future this work can contribute to assemble prototypical structures of molecular systems and the idea is these circuits could have much lower power consumption and reduce fabrication costs," said Gerhard Meyer, scientist, IBM Research, Zurich, in response to an e-mail query. "This is an important step, but one of many that will need to be achieved to build computing elements at the atomic scale. Techniques like self assembly might be used for manufacturing," he said.

How it's done
As described by IBM, the microscope uses a sharp metal tip to measure the tiny forces between the tip and the sample, such as a molecule, to create an image. Pentacene is an oblong organic molecule consisting of 22 carbon atoms and 14 hydrogen atoms measuring 1.4 nanometers in length. The spacing between neighboring carbon atoms is only 0.14 nanometers--roughly half a million times smaller than the diameter of a human hair, according to IBM.


To image the chemical structure of a molecule with an AFM, it is necessary to operate in very close proximity to the molecule. IBM scientists were required to keep the molecules from attaching to the tip when the tip was approached too closely.