Graphene has been a material of significant interest in the materials community for many years now. Separately, so have topological insulators, which have been observed in several 3D materials. Unfortunately, graphene does not inherently behave as a topological insulator because of carbon’s small intrinsic spin-orbit coupling. However, recent predictions for proximity induced spin-orbit coupling on graphene have led to the conclusion that it might be possible to make a topological insulator out of adatom-doped graphene. Here, we discuss the impact of tungsten adatoms on the electronic properties of monolayer graphene. Using a cryogenic probe, we have evaporated tungsten onto the surface of graphene devices. For dilute coatings, the adatoms are found to donate electrons to the graphene, becoming charged impurities that reduce the carrier mobility but do not form clusters. Interestingly, we find a large discrepancy between the expected density of adatoms when compared with the induced change in electron density. We hypothesize that this discrepancy is a consequence of a remnant layer of PMMA residues from device fabrication.
Graduate Student Seminars
Transport and Scattering in Tunsgten-decorated Graphene
Jamie Elias, Department of Physics, Washington University
February 24, 2017 at 4:15 pm