Doping of adsorbed graphene from defects and impurities in SiO ₂ substrates

Abstract

The performance of novel graphene-based devices often strongly depends on the electrical quality of the supporting oxide. To elucidate the general governing principles underlying this behavior, we use first-principles simulations to generate representative classes of experimentally known defect centers in passivated silicon dioxide substrates and study their charge transfer with adsorbed graphene. We find that many of the open-shell structural perturbations generated near the interface self-passivate during annealing, leading to occupied-unoccupied pairs of midgap states in the silicon dioxide band structure, but no doping of the graphene occurs. However, dangling bonds or paramagnetic defect centers stable to thermal annealing do lead to partially occupied midgap energy states that are energetically misaligned with the Dirac point of graphene allowing charge to flow to or from the carbon layer. In particular, dangling oxygen bonds in the oxide strongly p dope the graphene. We also study doping from charge donating impurities within the substrate lattice as these also act to limit the performance of graphene-based devices. © 2012 American Physical Society.