Characterization of graphene-substrate interactions using scanning tunneling microscopy

Graphene;Scanning Tunneling Microscopy;Vicinal Water;GaAs;Mica

He, Kevin

关键词: Graphene;    Scanning Tunneling Microscopy;    Vicinal Water;    GaAs;    Mica;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/44325/Kevin_He.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The unique electronic and physical properties of material interfaces provide a never-ending source of novel physics and potential applications. As our ability to observe and manipulate the world transitions from the macro to the micro and now to the nano and atomistic scales, understanding what goes on at various interfaces becomes ever more important. This is especially true for the new breed of two-dimensional materials and their poster child, graphene. Because of its two-dimensional nature, it is extremely difficult for graphene to exist as a standalone material, and thus it is usually attached to a substrate. The graphene-substrate interface can have a considerable effect on the overall system’s electronic properties, and we intend to elucidate those effects in this dissertation.We use the ultra-high vacuum scanning tunneling microscope to study the interface between monolayer graphene flakes and various technologically relevant semiconducting substrates (GaAs, InAs, Si) at room temperature. We observe an electronic semi-transparency effect where the substrate surface states appear to protrude through the graphene. We are also able to manipulate the substrate through the graphene and characterize the effects that this change in the substrate has on the graphene’s electronic properties. Besides studying graphene as an electronic material, we also demonstrate its use as a conductive coating for characterizing the volatile interface between water and mica at room temperature. Normally, we would not be able to image this surface in an ultra-high vacuum due to the vapor pressure of water, but the graphene is able to trap the water in place while preserving its original structure. This technique can also be expanded upon to study structures in water, such as carbon nanotubes and biological materials.