PHILADELPHIA - Physicists at the University of Pennsylvania have characterized an aspect of graphene film behavior by measuring the way it conducts electricity on a substrate. This milestone advances the potential application of graphene, the ultra-thin, single-atom thick carbon sheets that conduct electricity faster and more efficiently than silicon, the current material of choice for transistor fabrication.
The research team, led by A.T. Charlie Johnson, professor in the Department of Physics and Astronomy at Penn, demonstrated that the surface potential above a graphene film varies with the thickness of the film, in quantitative agreement with the predictions of a nonlinear Thomas-Fermi theory of the interlayer screening by relativistic low energy charge carriers. The study appears online in the journal Nano Letters and will appear in print in the August edition.
Johnson's study, "Surface Potentials and Layer Charge Distributions in Few-Layer Graphene Films," clarifies experimentally the electronic interaction between an insulating substrate and few-layer graphene films, or FLGs, the standard model for next-generation transistors.
It is more practical to develop devices from FLGs, rather than single-layer materials. To make use of these films, graphene must be placed on a substrate to be functionalized as a transistor. Placing the film on a substrate causes an electronic interaction between the two materials that transfers carriers to or from, or "dopes," the FLG.
The focus of the Penn study was aimed at understanding how these doped charges distribute themselves among the different layers of graphene. The distribution of these charges determines the behavior of graphene transistors and other circuits, making it a critical component for device engineering. The team measured the surface potential of the material to determine how these doped charges were distributed along the transistor, as well as how the
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University of Pennsylvania