First-principles study on the atomic and electronic structures of the Au/Si(111)-α(√3 × √3)R30° surface

Abstract

We have investigated the atomic and electronic structures of the Au/Si(111)-α(√3 × √3)R30° surface using the first-principles calculations within the density functional theory in the generalized gradient approximation, focusing on honeycomb configurations. The energetically favored honeycomb model has a geometry that two Au atoms are located at H₃ site on a Si substrate with missing top layer configuration. The formation energy of this model is less than that of the conjugate honeycomb-chained trimer (CHCT) one proposed by Ding et al. [Surf. Sci., 275, L691 (1992)] and that of the most stable configuration having the Au coverage of 1/3 ML in a certain range of chemical potential of Au. The observed energy band structure is not completely reproduced in our calculation using the honeycomb configuration as well as the CHCT one. On the other hand, the scanning tunneling microscope image simulated for the stable honeycomb model agrees with the observed ones. Our results, together with the recent experimental evidence that the Au coverage of the surface is less than 1 ML, suggest that the honeycomb configuration is more plausible than the CHCT one, which has been considered to be most suitable for the atomic structure of the commensurate region in the surface. [DOI: 10.1380/ejssnt.2004.146]