The valence-band and the O 2s core-level spectra of ultrathin (about 1 nm) SiO2 layers [which are formed at the initial stages of oxidation of hydrogen-terminated Si(100) substrates] were measured by high-resolution x-ray photoelectron spectroscopy. The energy difference between the valence band and the core level was found to be greater than that for the bulk SiO2. A first-principle molecular-orbital calculation was performed on Si2O7H6 clusters in order to obtain the energy difference (which depends on the structure of SiO2 layers). A comparison of the experimental data and the molecular-orbital calculations indicates that the intertetrahedral bond angle, θSi-O-Si, is 135° to 140° in the SiO2 structural transition layers at the SiO2/Si interfaces.
|ジャーナル||Physical Review B - Condensed Matter and Materials Physics|
|出版ステータス||Published - 1999|
ASJC Scopus subject areas