First-principles study of one-dimensional quantum-confined H-passivated ultrathin Si films

An ab initio study of the electronic structure of the one-dimensional quantum-confined H-passivated crystalline ultrathin Si in large thickness range of 2.7–27.0 Å has been made, employing a self-consistent full potential linear muffin-tin orbital (FPLMTO) method along with the density functional theory in local approximation. Calculations have been performed for a quite big unit cell with sufficient separation between the unit cells to avoid interference effects between the two surfaces of a unit cell as well as between the two successive unit cells. The present results show the absence of overlocalized states in quantum-confined systems and the occurrence of the extended states responsible for the luminescence observed in quantum-confined nanostructures. The presently calculated values of the band gap show an exponential rise with a decrease in the quantum-confined size in the ultrathin film region. The present results have been obtained for a more extended film thickness region as compared to earlier ab initio calculations.