Functional electrical contacts to two-dimensional materials with tunable interfacial oxides
Two-dimensional (2D) van der Waals (vdW) materials are promising for future nanoelectronic devices. However, their performance is often hampered by the presence of a large number of defects at metal/2D material interfaces. The project ProTOC will extend the applications of atomic layer deposition (ALD) to engineer functional electrical contacts in 2D nanoelectronic devices using interfacial transition metal oxides (TMOs) of controlled stoichiometry and electronic properties. ALD-grown TMOs, vanadium and titanium oxides, are explored as interfacial layers that are vdW-bonded to 2D material MoS2 on one side and chemically bonded to the metal electrode one the other side. ALD allows for precise control of the oxide composition in order to tune electronic properties, such as work function, dielectric constant, and defect concentrations. The electronic properties of ultrathin ALD-oxides of different compositions and their complex interactions with 2D materials, which in turn affect transport, will be investigated in a combined effort using 2D field-effect transistor (FET) transport measurements, spectroscopic methods, and scanning probe microscopy techniques. The band alignment at the contacts can be adjusted by changing the composition of the ALD-grown layers, which may provide a new route to engineering desired contact behaviour over a broad range from rectifying or low resistance ohmic, depending on the end application. This contacting scheme will be exploited to achieve both p- and n-type conductance in MoS2 FETs, which is key for logic applications and difficult to achieve with 2D materials. This project will benefit from the complimentary knowledge and experience of researcher, who is an expert in device design, fabrication, and advanced scanning probe methods, as well as host, who provides unique capabilities and expertise in materials growth by ALD and the spectroscopic characterization of complex oxide films in the context of devices.