Silicon oxynitride and silicon oxynitride-silicon interface: a photoemission study

A study of silicon-oxynitride materials and their interfaces with amorphous silicon using synchrotron radiation photoemission is discussed. The effect of the hydrogen atoms as an intralayer at the silicon-oxynitride-a-Si interface is also analyzed. The data relative to the bulk silicon oxynitride show that the valence band edge gradually shifts toward a higher binding energy as the [O]/[N] ratio (A) is increased. For the silicon-oxynitride-a-Si heterojunctions, the valence band discontinuities ΔE_v ranged from 1.1±0.15 eV in the case of A=0.08 up to 4.6±0.15 eV in the case of A=2.02. The effect of the hydrogen intralayer was to reduce the ΔE_v by 0.5±0.15 eV. The observed intralayer-induced effect is attributed to modification of the interface dipoles. A simple model calculation, based on electronegativity arguments, gives a reduction of 0.4 eV for A=0 and 0.46 for A corresponding to pure silicon dioxide (SiO₂)