Atomic and electronic structure ofβ−SiC(001)−(3×2)

A reconstruction model for the cubic $\mathrm{SiC}\mathrm{}\left(001\right)\mathrm{}-(3\mathrm{}\times 2)$ surface, which we call two adlayer asymmetric-dimer model (TAADM), is suggested on the basis of ab initiopseudopotential total energy and grand canonical potential calculations. Within this model, two Si adlayers with a nominal total coverage of one monolayer are adsorbed on the clean Si-terminated surface. Asymmetric dimers are formed in the top adlayer with a dimer-bond length of 2.24 Å. This reconstruction model overcomes all shortcomings of previous models, such as the single-dimer-row, alternate-dimer-row, and double-dimer-row models, and it is the most stable structure among all configurations which we have considered. The calculated surface-band structure, as well as the filled- and empty-state scanning tunneling microscope images for our TAADM, are in very good agreement with experimental observations.