A high-resolution core-level photoemission study of the Au/4H-SiC(0001)-(root 3 x root 3) interface

We present a systematic study of different reconstructions obtained after deposition of Au on the (root 3 x root 3)- R30 degrees- 4H- SiC( 0001) surface. For 1-2 monolayers ( ML) Au and annealing temperature T-anneal similar to 675 degrees C, a 3 x 3 reconstruction was observed. For 4 ML Au and T-anneal similar to 650 degrees C, a ( 2 root 3 x 2 root 3)- R30 degrees. reconstruction appeared, while 5ML Au annealed at 700 degrees C reconstructed to give a ( 6 root 3 x 6 root 3)- R30 degrees. pattern. From the Si 2p and Au 4f core- level components, we propose interface models, depending on the amount of Au on the surface and the annealing temperature. For 1 - 4 ML Au annealed at 650 - 675 degrees C, gold diffuses under the topmost Si into the SiC and forms a silicide. An additional Si component in our Si 2p spectra is related to the interface between the silicide and SiC. For 5 ML Au annealed at 700 degrees C, silicide is also formed at the surface, covering unreacted Au on top of the SiC substrate. The interface Si component is also observed in the Si 2p spectra of this surface. The key role in Au/root 3- 4H- SiC( 0001) interface formation is played by diffusion and the silicon- richness of the surface.