Electronic Structure of Li, Be, and Al Ultrathin Coverings on the Si(100) Surface

Abstract

Within the framework of density functional theory and the pseudopotential method, calculations of the density of electronic states of the system “Si(100) substrate plus disordered two-dimensional metal layers (Li, Be or Al)” with a thickness of one to four single-atomic layers were carried out during growth at 0°K. It is shown that the electronic structure of the first single-atomic layers of these metals on Si(100) has band gaps. The maximum band gap was found in the Be-Si system (1.03 eV for a single-atomic layer). In this system, the band gap disappears when four single-atomic layers are deposited. In the Li-Si system (0.98 eV for a single-atomic layer) it disappears for two single-atomic layers. In the Al-Si–system (0.50 eV with four single-atomic layers), the band gap disappears for three single-atomic layers. This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.