Using electrostatic force microscopy measurements, the team characterized the surface potential of the graphene film and found it to be dependent on the thickness of the graphene layers. The thicker the carbon strips, the higher the electronic surface potential, with the surface potential approaching its limit for films that were five or more sheets thick. This behavior is unlike that found for conventional metals or semiconductors which would have, respectively, much shorter or longer screening lengths.
The surface potential measurements were in agreement with a theory developed by Penn professor and physicist Eugene Mele. The theory makes an important approximation, by treating electrostatic interactions in the film but neglecting quantum mechanical tunneling between neighboring layers. This allows the model to be solved analytically for the charge distribution and surface potential.
While prior theoretical work considered the effect of a substrate on the electronic structure of FLG, few experiments have directly probed the graphene-substrate interaction. Quantitative understanding of charge exchange at the interface and the spatial distribution of the resulting charge carriers is a critical input to device design.
Graphene-derived nanomaterials are a promising family of structures for application as atomically thin transistors, sensors and other nanoelectronic devices. These honeycomb sheets of sp2 -bonded carbon atoms and graphene sheets rolled into molecular cylinders share a set of electronic properties making them ideal for use in nanoelectronics: tunable carrier type and density, exceptionally high carrier mobility and structural control of their electronic band structures. A significant advantage of graphene is its two-dimensionality, making it compatible with existing planar device architectures. The challenge is realizing t
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University of Pennsylvania