Time Dependence of the Metastable, Optically-Induced ESR in a-Si:H

Abstract

The occurrence of optically-induced, metastable changes in the paramagnetism in films of a-Si:H is well known. The effect was first observed with white light in powdered samples, but recent experiments with both white and monochromatic light incident on films on substrates have observed a similar effect. This optically-induced ESR appears to be stable at temperatures ≤ 400 K. Typical inducing curves for samples with initial dark spin densities n_s > 10¹⁶ spins/cm³ approach a power law behavior (n_s ∼ t^1/3) at long times. However, when the dark spin density is less than 10¹⁶ spins/cm³, the samples exhibit an inducing curve (on a log-log scale) with a continuously decreasing slope. The curve does not exhibit a unique power law behavior over an extended range of time and is at all times ≤ t^1/3.