Nitrogen-bonding environments in glow-discharge—deposited a − Si : H films

We have studied the local bonding of nitrogen atoms in glow-discharge\char22{}deposited films of $a\ensuremath{-}\mathrm{Si}:\mathrm{H}$ by using ir absorption spectroscopy. We find two different bonding environments for N, which are identified through different frequencies for the Si-N asymmetric bond-stretching vibration, 840 ${\mathrm{cm}}^{\ensuremath{-}1}$ for the high-${T}_{s}$ films, and 790 ${\mathrm{cm}}^{\ensuremath{-}1}$ for the low-${T}_{s}$ films. In films deposited on substrates held at temperatures in excess of 300\ifmmode^\circ\else\textdegree\fi{}C, the N is incorporated in a planar site with three silicon nearest neighbors, and one hydrogen second-nearest neighbor. In films produced on substrates held below 200\ifmmode^\circ\else\textdegree\fi{}C, the N atom is also in a threefold-coordinated planar site, but with all of the nearest and second-nearest atoms being Si atoms.