Transition from amorphous to microcrystalline Si:H:: effects of substrate temperature and hydrogen dilution

Structural changes in silicon films with variations of hydrogen dilution and substrate temperature have been studied. At a critical value of hydrogen dilution in silane (phi) a sharp transition from amorphous to microcrystalline phase has been observed. An increase of substrate temperature from 170 to 340 degreesC shifts the transition point from phi = 95.5% to 93.5%. The change in dark conductivity and absorption corroborate with the change in crystalline volume fraction in the films. The grain size varies from 45 to 360 Angstrom depending on deposition conditions. Optical absorption and hydrogen content in the film decreases drastically with formation of microcrystalline structure. Silicon films developed at 340 degreesC show moderate photosensitivity together with low light induced degradation at low crystallinity, which might be suitable properties for solar cell application. (C) 2002 Elsevier Science B.V. All rights reserved.