Adsorption of Al on the Si(0 0 1) surface

The first-principles calculations have been presented to study the adsorption of aluminum (Al) on the Si(0 0 1)(2×1) surface. We have investigated the optimized geometries and electronic structures of the adatom–substrate system. The adsorption energy of the system has been calculated. The most stable adsorption sites were consequently determined to be HH site and T3+T4. It is shown that the Si–Si dimer is asymmetric on the reconstructed bare surface and become symmetric upon Al adsorption. In addition, the bond length of Si–Si was found to be considerably elongated in the adsorption system. It is found that the work function change obtained in our work is different from other previous results on the adsorption of alkali metals on the Si(0 0 1) surface. In order to investigate the relative stability of phases at different coverages, the surface formation energy of the adsorption system was calculated. To shed light on the nature of the Al–Si bond and the character of silicon surface, the density of states (DOS) and difference charge density of the system were evaluated.