Hydrogenated amorphous silicon(a-Si:H) and hydrogenated micro-crystalline silicon(μc-Si:H) thin films were deposited on glass, [100] single crystal silicon wafer with thermally grown silicon dioxide, and [100] single crystal silicon wafer substrates by Plasma Enhanced Chemical Vapour Deposition with argon diluted silane source gas. The analysis of the deposited films with XRD pattern, RAMAN scattering profile and TEM photograph showed that a-Si:H and μc-Si:H films can be deposited alternatively by varying substrate temperature and r.f. power. Optical band gap, dangling bond density and the hydrogen quantity in the deposited films have been investigated as a function of the preparation conditions by measuring UV-absorbency, electron spin resonance signal, and FT-lR transmittance.
The micro-crystalline fraction increases with the increase in the r.f. power, and shows a maximum with the increase in the substrate temperature. The optical band edge of the deposited films shifts to blue with the increase in the r.f. power and shifts to red with the increase in the deposition temperature.
The amorphous phase deposited at high substrate temperature possesses low hydrogen density and high dangling bond density. The increase in the substrate temperature varies the hydrogen bonding mode from Si-$H_2$ to Si-H. The amorphous phase deposited at low substrate temperature and low r.f. power contains lots of hydrogen and small number of dangling bonds. The hydrogen bonding mode varies from Si-H to Si-$H_2$ with the increase in the r.f. power.
