The Valence Band Tail Density of States and Bond Angle Distortion in a-SiNx: H Alloys

Abstract

AbstractFilms of a-SiNx:H with x = 0.0..0.62 were deposited by glow discharge decomposition of (10% SiH4+90%/H2 )+ NH3 mixture. The chemical bonding and composition of films were investigated with using of infrared spectroscopy. The deformation energy per Si atom connected to bond bending Vkθ was calculated from data of Raman scattering. Characteristic energy of valence band tail (VBT) states distribution, E0v, were determined fromrsubgap absorption spectra. The dependencies of E0v and Vkθ on film composition, x, were considered in order to estimate the influence of the bond angle disorder on the distribution of VBT states.The essential difference in behavior of E0v and Vkθ dependencies on x was found for Si-rich (x<0. 15) alloys. When Vkθ value increase with x, the E0v parameter stays almost constant; while at x>0. 15 the E0v increase with x as well as the VKO. It means that bond angle disorder in the bulk of the material contributes to VBT characteristic energy, but it is not the only source. Another factors as it was shown may be connected with valence states of Si atoms, localized near inner boundaries.