Local bonding structures of SiO2 films on H-terminated Si(100) surfaces studied by using high-resolution electron energy loss spectroscopy

We have investigated the relaxation in the structure of Si-O-Si bonds and the bonding states at high temperatures of Si-H and Si-D after the oxidation of H- and D-terminated Si(100) surfaces by using high-resolution electron energy loss spectroscopy (HREELS). The results of H(D) desorption from SiO2 formed on H(D)-terminated Si surfaces indicate that the Si-H(D) bonds of 2O-Si-2H(2D) species are stable compared with those of O-Si-2H(2D). A central-force-network model was used and it was found that the structural relaxation of Si-O-Si bonds on 2.7-monolayer (ML)-thick SiO2 films becomes high with an increase in the annealing temperature. However, the force constant of thermal SiO2 grown at 700 degrees C is higher than that of low-temperature SiO2 annealed at the same temperature. Moreover, the farce constant is almost independent of the SiO2 thickness and the oxidation process above 2 ML. Consequently, the force constant is governed by the oxidation temperature. In addition, the Si-O-Si structure is hardly relaxed during annealing for 5 min when the thickness of SiO2 films is being increased. (C) 1998 Elsevier Science B.V. All rights reserved.