Photoluminescence and Raman studies in thin-film materials: Transition from amorphous to microcrystalline silicon

We measured photoluminescence (PL) and Raman spectra for films deposited by hot-wire chemical vapor deposition using various hydrogen to silane ratios . We observed: (a) a PL peak energy increase from 1.25 to 1.4 eV as the mat erial approaches the a- to mu c-Si transition region; (b) a dual-PL peak at 1.3 and 1.0 eV for the film with a H dilution ratio of 3; and (c) as the H ratio increases, the 1.3 eV PL fades away and the low energy PL dominates. Meanwhile, a redshift of the peak position, a decrease of the intensity, a nd a narrower bandwidth for the low energy PL are also observed. The low en ergy PL is explained by band-tail radiative transitions from two types of g rain boundaries. (C) 1999 American Institute of Physics. [S0003-6951(99)027 27-8].