Stability, reconstruction, and surface electronic states of group-III atoms on SiC(111) - art. no. 165308

The adsorption of 1/3 monolayer of the group-III elements B, Al, Ga, and In on a Si-terminated SiC(111) root3 x root 3R30 degrees surface is investiga ted in dependence on the surface preparation conditions using the density f unctional theory (DFT). The energetics, the bonding behavior and the result ing surface electronic structure are studied and chemical trends are derive d. For the metal atoms Al, Ga, and In the replacement of a Si atom in a T-4 position always gives the most stable configuration. The first-row element B shows a completely different behavior. Under Si-rich conditions boron re places a second-layer C atom in a S-5 position, whereas under C-rich condit ions a first-layer Si atom is replaced by boron. The different adsorbate co nfigurations result in completely different surface electronic structures. Al, Ga, and In adsorption passivates the surface. The fundamental gap is vi rtually free from empty or occupied surface states. The B adsorption in the S-5 configuration follows this behavior. However, boron substituting a Si- atom gives rise to an empty midgap surface band.