The effect of vacuum annealing on local structure reconstruction, evolution of photoluminescence  and paramagnetic defects in C-rich a-Si1−xCx:H films (x = 0.7) was studied. Strong enhancement of visible (white-green) photoluminescence was observed after annealing at 400 to 500C. Such enhancement was correlated with increasing of the concentration of C-hydrogen bonds in Si:C-Hn accompanied with increase in the fluctuation of the interatomic potential. Complete disappearance of photoluminescence, “graphitization” of the C precipitates, and a strong increase in the concentration of the paramagnetic states were observed after annealing at 650C and above. The enhancement and the degradation of photoluminescence after different-temperature treatments were explained by the following competing effects: (1) enhancement of the radiative recombination due to passivation of paramagnetic defects with H and increase of localization of photo-excited electron-hole pairs due to formation of new Si:C-H and (2) enhancement of the non-radiative recombination through the paramagnetic states due to increase in their concentration caused by graphitization of C precipitates after high- temperature treatment.

Structure, Paramagnetic Defects and Light-Emission of Carbon-Rich a-SiC:H Films. A.V.Vasin, S.P.Kolesnik, A.A.Konchits, A.V.Rusavsky, V.S.Lysenko, A.N.Nazarov, Y.Ishikawa, Y.Koshka: Journal of Applied Physics, 2008, 103[12], 123710