Structure and optical properties of a-Si1−xNx:H alloys

The optical spectra (1–10 eV) of plasma deposited films of a-Si1−xNx:H have been studied in the range 0≤x≤0.57 (stoichiometric a-Si3N4:H). It is found that up to x=0.3 the dielectric function ∈2(ω) is mainly determined by the concentration of SiSi bonds. For x>0.3 the number of SiSi bonds becomes too small to allow the existence of a connected Si-network and the spectra reveal the contribution of Si-N bonds at higher energy. This change from Si-like to SiNi-like behavior occurs when about 60 % of the SiSi bonds have been substituted which is close to the threshold for bond percolation in a tetrahedral network.