Photoluminescence characteristics of amorphous slicon nitride nanoball film prevented from oxidizing in air

Hydrogenated amorphous silicon (a-Si : H) nanoball film emits photoluminescence only after being thermally oxidized, because the oxidized film is sufficiently transparent that excitation laser light can reach Si nanocrystal. We fabricated amorphous silicon nitride (a-SiNH) nanoball film by reacting N ₂ plasma and SiH4 gas. Without being thermally oxidized, this film was highly transparent and exhibited photoluminescence. The source of this photoluminescence is presumed to be either the quantum size effect of Si nanocrystal or electronic transitions in siloxane (Si-O-Si), which is present at the interface between Si nanocrystal and SiO ₂. By coating the a-SiNH nanoball film with SiN film, we fabricated a-SiNH nanoball film that was siloxane-free but that exhibited photoluminescence. Hence, we attribute the observed photoluminescence to the quantum size effect of Si nanocrystal.