Impurity Diffusion Barrier Effect of Ultra-Thin Plasma-Nitrided a-Si:H Overlayer on SnO2/Glass Substrate

Tin diffusion into p-type a-Si1-xCx:H (x=0.28) deposited on an SnO2/glass substrate has been significantly reduced by employing an ultra-thin plasma-nitrided a-Si3N4:H barrier layer inserted between a-Si1-xCx:H and SnO2. It is shown that the a-Si3N4:H layer is very uniform to prevent Sn diffusion and that reduced Sn atoms form chemical bonds with Si, C and N in the a-Si1-xCx:H/a-Si3N4:H/SnO2 interfaces. The reduced Sn atoms bonded to Si, C, or N tend to increase the density of states in the a-Si1-xCx:H valence band tail near the Fermi level.