The diffusion of oxygen atoms on graphene and its dependence upon the carrier density controlled by a gate voltage were analyzed. Density functional theory was used to determine the equilibrium adsorption sites, the transition state, and the attempt frequency for different carrier densities. The ease of diffusion was strongly dependent on carrier density. For neutral graphene, a barrier of 0.73eV was calculated. Upon electron doping, the barrier decreased almost linearly to reach values as low as 0.15eV for densities of 7.6 x 1013/cm2. This implied an increase of more than 9 orders of magnitude in the diffusion coefficient at room temperature. This dramatic change was due to a combined effect of bonding reduction in the equilibrium state and bonding increase at the transition state and could be used to control the patterning of oxidized regions by an adequate variation of the gate voltage.

Gate-Voltage Control of Oxygen Diffusion on Graphene. Suarez, A.M., Radovic, L.R., Bar-Ziv, E., Sofo, J.O.: Physical Review Letters, 2011, 106[14], 146802