EMISSION PROPERTIES OF AMORPHOUS-SILICON AND CARBON-FILMS

We present novel results on the emission properties in amorphous silicon and carbon films with the emphasis on the carbon films. Amorphous carbon films show a strong photoluminescence in the visible region at room temperature. The temperature dependence of PL both in a-Si:H and a-C:H films has been studied. The films of a-C:H show a slower temperature quenching rate compared to a-Si:H. Superlinear behavior of PL intensity as a function of excitation intensity has been observed both in a-C:H and a-C films. The PL peak position E(L) shows a dramatic blue-shift as the excitation intensity increases. A large red-shift of E(L) has been found as the excitation energy drops below a certain value. These phenomena can be qualitatively explained by considering the electronic structure of the disordered system and the different type of transitions of photo-excited carriers in the band tail states.