Calculations of the electronic structure of diamond (001) ultrathin films

Abstract

The electronic structure of (001) quantum films of diamond (C) is calculated by the extended Hückel-type non-orthogonal tight-binding method. It is found that the C(001) ultrathin films studied are semiconductors having a direct gap at the centre of the surface Brillouin zone, and that the conduction band minimum (CBM) of the film is around the bulk CBM independent of film thickness, whereas the confinement energy of the valence band maximum of the film is increased with decreasing film thickness. It is shown that the lowest optical transitions across the band gap in the C(001) ultrathin films studied are dipole allowed and that their oscillator strengths are significantly higher than those for the Si counterparts.