In hydrogenated amorphous Si the kinetics of the optically induced production and thermal annealing of Si dangling bonds were measured between 25 and 480K using electron spin resonance. Below about 150K the measurement of optically induced Si dangling bonds was masked by long-lived, band-tail carriers that accumulate with time as

t1/3. It was known that these long-lived carriers could be quenched by infra-red light. However, optically, it was not possible to remove them completely. The production rate for optically induced Si dangling bonds decreased with decreasing temperature. Below about 100K degradation was at most half as efficient as at room temperature and was nearly temperature independent below approximately 100K. Additionally, defects created by 10h of irradiation below 100K almost entirely anneal at about 300K. It was common procedure to anneal (175C, 0.5h) a-Si:H samples in order to restore the as-deposited defect density. However, by repeatedly performing degradation and annealing cycles it was found that a small fraction of defects was not restored by annealing at 175C and that these defects slowly accumulate with degradation. For defects created at all temperatures, the same electron spin resonance fingerprint was found; indicating that only one dominant type of defect was created, presumably the Si dangling bond, and it was concluded that different, temperature-dependent stabilization processes had to exist. These results led to new constraints for models that attempt to explain the Staebler-Wronski effect.

Temperature Dependence of the Optically Induced Production and Annealing of Silicon Dangling Bonds in Hydrogenated Amorphous Silicon. N.A.Schultz, P.C.Taylor: Physical Review B, 2002, 65[23], 235207 (8pp)