The theoretical DFT study of electronic structure of thin Si/SiO2 quantum nanodots and nanowires

The atomic and electronic structure of a set of proposed thin (1.6 nm in diameter) silicon/silica quantum nanodots and nanowires with narrow interface, as well as parent metastable silicon structures (1.2 nm in diameter), was studied in cluster and PBC approaches using B3LYP/6-31G* and PW PP LDA approximations. The total density of states (TDOS) of the smallest quasispherical silicon quantum dot (Si85) corresponds well to the TDOS of the bulk silicon. The elongated silicon nanodots and 1D nanowires demonstrate the metallic nature of the electronic structure. The surface oxidized layer opens the bandgap in the TDOS of the Si/SiO2 species. The top of the valence band and the bottom of conductivity band of the particles are formed by the silicon core derived states. The energy width of the bandgap is determined by the length of the Si/SiO2 clusters and demonstrates inverse dependence upon the size of the nanostructures. The theoretical data describes the size confinement effect in photoluminescence spectra of the silica embedded nanocrystalline silicon with high accuracy.Comment: 22 pages, 5 figures, 1 tabl