Berlin 2018 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 14: 2D Materials: Session II (joint session DS/CPP/HL)
HL 14.3: Vortrag
Dienstag, 13. März 2018, 10:00–10:15, H 2032
Gate-Dependent Vacancy Migration in Graphene — •Rohit Babar1 and Mukul Kabir1,2 — 1Department of Physics, Indian Institute of Science Education and Research, Pune, India — 2Center for Energy Science, Indian Institute of Science Education and Research, Pune, India
Graphene based ultrathin devices offer significant advantage due to their high carrier mobility and a gate-tunable carrier density. However, the experimental observations of vacancy diffusion near room-temperature can potentially lead to undesirable void formation and/or edge modification of such devices. Combining transition state theory with first-principles method, we investigate the microscopic vacancy migration mechanism in graphene and its dependence on gate voltage. The intrinsic vacancy diffusion involves a concerted motion of atoms along with an out-of-plane displacement, which is unique to graphene compared with other 2D materials. We further investigate the migration mechanism under gate voltage and find that the activation barrier non-monotonically increases for both electron and hole doping. The trend in activation barrier is explained via collective-phonon stiffening. We estimate a 107-fold decrease in vacancy diffusivity at room temperature. Thus, our findings reveal that the graphene-based devices will not degrade further under device operating condition through vacancy migration.