Anomalous Diffusion of Hydrogen and the Dependence of the Diffusion Constants on Hydrogen Content in Hydrogenated Amorphous Silicon

Abstract

ABSTRACTThe diffusion constant of hydrogen DH(t) in hydrogenated amorphous silicon (a-Si:H) is strongly dependent on the Si-bonded H content CH of the films. It increases by over four orders of magnitude for CH ranging from 1 to 19 at. %. In an rf sputter-deposited film of CH ∼5 at. % it increases with time at 300 ≤ T ≤ 362°C. The dispersion parameter α in DH(t) = D∞ (ωt)-αis thus negative. This observation and the increase of α with T above a sample-dependent temperature Tτ are discussed in relation to low temperature structural relaxation processes in the amorphous network.