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 quant um-confined H-passivated crystalline ultrathin Si in large thickness range of 2.7-27.0 Angstrom has been made, employing a self-consistent full potent ial linear muffin-tin orbital (FPLMTO) method along with the density functi onal theory in local approximation. Calculations have been performed for a quite big unit cell with sufficient separation between the unit cells to av oid interference effects between the two surfaces of a unit cell as well as between the two successive unit cells. The present results show the absenc e of overlocalized states in quantum-confined systems and the occurrence of the extended states responsible for the luminescence observed in quantum-c onfined nanostructures. The presently calculated values of the band gap sho w an exponential rise with a decrease in the quantum-confined size in the u ltrathin film region. The present results have been obtained for a more ext ended film thickness region as compared to earlier ab initio calculations. (C) 2000 American Institute of Physics. [S0003-6951(00)05145-7].