VARIATIONS OF THE LOCAL-DENSITY OF ELECTRON-STATES AND SHORT-RANGE ORDER IN AMORPHOUS HYDRATED SILICON FILMS

Ultrasoft x-ray spectroscopy methods have been used to observed a chan ge in the energy distribution of the silicon valence states after anne aling a-Si:H films at 500 degrees C. This change appears as three dist inct maxima in the density of states 3.5, 7.2, and 10.2 eV above the t op of the valence band, which indicates ordering of the a-Si:H structu ral network. The energy distance between the latter two maxima (E-E-up silon=7.2 and 10.2 eV) supports electron-diffraction data indicating a decrease in the silicon-silicon interatomic distance by 0.2 Angstrom in comparison with the crystal. The presence of a third maximum (E-E-u psilon=3.5 eV) is connected with the change in the hybridization of th e s-p-functions of silicon with decrease of the coordination number. ( C) 1997 American Institute of Physics.