Graphene on the oxidized SiC surface and the impact of the metal intercalation

Abstract

We have performed first-principles calculations of the structural and the electronic properties of graphene (G) adsorbed (i) on the oxidized SiC surface (G/X/SiC, with X = Si2O3, Si2O5, and OH), and (ii) on the metal (M = Au and Al) intercalated Si2O5 silicate layer, G/(M)Si2O5/SiC. In (i), we focused on the structural characterization of the oxidized surface, based on a set of simulations of the X-ray absorption spectroscopy (XAS). We found that the XAS features are slightly modified upon the presence of the graphene layer, which can be attributed to the net charge transfers from the graphene sheet to the oxidized SiC surface. Such a p-type doping of graphene is larger by the presence of C dangling bonds (DBs), namely G/Si2O3/and G/Si2O5/SiC(0001¯). In (ii), we show that (M)Si2O5/SiC is an interesting platform to perform band engineering based on G/SiC interface. Through a proper combination of surface states and external electric field, we found the formation of ohmic contacts at the G/(M)Si2O5 interface; namely p-type [n-type] ohmic contact in G/(Au)Si2O5/SiC(0001¯) [G/(Al)Si2O5/SiC(0001)] with the excess of electrons [holes] on the metal induced surface states, giving rise to (tuneable) metallic channels localized in the metal doped silicate monolayer, (M)Si2O5, on top of the SiC surface.