Gate dependent vacancy diffusion in graphene

Rohit Babar, Mukul Kabir

Published 2018-03-12Version 1

Kinetics of vacancy defect in graphene drives structural modifications leading to disorder, multi-vacancy complex and edge reconstruction. Within the first-principles calculations, we investigate the dynamic Jahn-Teller distortion and vacancy diffusion with different carrier doping. The experimental observation of dynamic Jahn-Teller distortion is argued to be blocked by defect functionalization and charge doping. We demonstrate that lattice relaxation perpendicular to the graphene sheet and in-plane strain relaxation play the predominant roles in predicting the correct microscopic mechanism for vacancy diffusion and thus the accurate activation barrier. The importance of quantum correction to the classical barrier is discussed. Further, the calculated activation barrier increases upon both electron and hole doping and the observed trends are explained by the differential charge density and by the hardening of the low-energy phonon modes that are responsible for vacancy diffusion. Electron doping essentially freezes the vacancy, and thus any degradation mediated by it through a dramatic decrease in diffusivity. While tracking vacancy diffusion experimentally in graphene is a difficult task, the present results will motivate new experimental efforts and assist interpretation of the results.