摘要 : This paper reports the effect of annealing on hydrogenated amorphous silicon films (a-Si:H) deposited by r.f. self-bias technique on cathode in an asymmetric r.f. plasma CVD system at room temperature. Detailed study of the variat... 展开 This paper reports the effect of annealing on hydrogenated amorphous silicon films (a-Si:H) deposited by r.f. self-bias technique on cathode in an asymmetric r.f. plasma CVD system at room temperature. Detailed study of the variation of the dark and photoconductivity (σ_D and σ_(ph)) as a function of temperature and light intensity, surface morphology, hydrogen evolution, optical absorption, subgap absorption and related parameters, thermal and structural disorder on the optical-absorption edge, IR vibrational modes and bonded hydrogen content have been carried out on unannealed and annealed samples at different temperatures (T_a) from 100 °C to 550 °C. It is found that the values of σ_(ph) increase and that of Urbach energy (E_o), subgap defect density (N_d) and the polyhydride to monohydride ratio decrease upto T_a = 250 °C and beyond 250 °C the values of σ_(ph) decrease and that of E_o, Nd and the polyhydride to monohydride ratio increase. The best opto-electronic properties with much improved σ_(ph) and σ_(ph)/σ_D and dominant monohydride bonding are obtained after annealing the room temperature deposited film at 250 °C for 1 h. The σ_D data obeys a Meyer Neldel rule in annealed a-Si:H films. The value of optical band gap is found to be related to the E_o and the hydrogen content. The Urbach energy (E_o) which is a measure of the disorder is the sum of structural and thermal disorder. The structural disorder part decreases with the annealing temperature upto approximately 300 °C and thereafter it increases. The curves of optical absorption coefficient versus photon energy at different Ta converge to a common point. 收起