NMR probe of band tail states in a-Si:H

Abstract

We measured the dipolar spin–lattice relaxation time ( T 1d) of the bonded hydrogen in hydrogenated amorphous silicon at low temperature. At 15 K, after the sample is irradiated by λ=6500 A ̊ light for 2 s, T 1d is reduced by about one order of magnitude. The reduction of T 1d is attributed to the cross-relaxation between the hydrogen and localized paramagnetic band tail states that are induced by the light. Within experimental error, T 1d is proportional to the inverse of the square of the density of the paramagnetic states, consistent with a previously proposed model.