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-resol ution electron energy loss spectroscopy (HREELS). The results of H(D) desorption from SiO2 formed on H(D)-terminated Si surfaces indicate th at 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 wa s found that the structural relaxation of Si-O-Si bonds on 2.7-monolay er (ML)-thick SiO2 films becomes high with an increase in the annealin g temperature. However, the force constant of thermal SiO2 grown at 70 0 degrees C is higher than that of low-temperature SiO2 annealed at th e same temperature. Moreover, the farce constant is almost independent of the SiO2 thickness and the oxidation process above 2 ML. Consequen tly, the force constant is governed by the oxidation temperature. In a ddition, the Si-O-Si structure is hardly relaxed during annealing for 5 min when the thickness of SiO2 films is being increased. (C) 1998 El sevier Science B.V. All rights reserved.