Thin films of hydrogenated silicon are prepared by varying the filament temperature (T(F)) (1600-1900 degrees C) at a deposition rate of 8-12 angstrom/s without using any hydrogen dilution. While the films deposited at low T(F) are amorphous in nature, those deposited at higher T(F) (>= 1800 degrees C) contain nanocrystallites embedded in the amorphous network. The optical band gap (E(04)) of the films (similar to 1.89-1.99 eV) is slightly higher compared to the regular films, which is attributed to the improved short and medium range order as well as the presence of low density amorphous tissues in the grain boundary regions. The films show improved stability under long term light exposure due to more ordered structure and presence of hydrogen mostly as strong Si-H bonds. (C) 2011 Elsevier B.V. All rights reserved.