ELECTRONIC-STRUCTURE OF THE DAS MODEL FOR THE SI(111)7X7 RECONSTRUCTED SURFACE BY ENERGY-BAND CALCULATIONS

Electronic structure of the dimers adatoms and stacking fault (DAS) model for the Si(111)7 x 7 reconstructed surface is theoretically investigated. A standard scheme with norm-conserving pseudopotential and local density approximation is applied in the repeated slab geometry. Surface states due to three kinds of dangling bonds are obtained: (1) of the adatoms, (2) of the first layer atoms, and (3) of the corner hole atoms. The local densities of states have been calculated at these dangling bond sites. For the adatom dangling bond states, pronounced asymmetry is found between the faulted and unfaulted parts of the unit cell. The obtained local densities of states are compared with the measured scanning tunneling spectroscopy (STS) data and with the photoemission spectra. Qualitative agreement has been obtained between the experimental results and the theory.