The relation between microstructure and hydrogen content and evolution for hydrogenated amorphous silicon films prepared by magnetron sputtering

Abstract

Amorphous hydrogenated silicon films have been prepared by reactive magnetron sputtering under a variety of preparation conditions. The hydrogen profile for the films measured by an improved 15N bombardment technique shows that hydrogen (H/host) percentages up to 50 can be obtained independent of the film microstructure. The hydrogen partial pressure has the greatest effect on the total hydrogen content. Hydrogen evolution spectra show that smooth films with uniform densities have relatively more complex evolution spectra and evolve proportionately less hydrogen at low temperatures than films with columnar structures. Thermodynamic and diffusion parameters are calculated from hydrogen evolution experiments in the range 20–700 °C. Parameter values are typical, ΔG ~ 1.4–2.1 eV, but low values for ΔH ~ 0.4–0.7 eV are calculated for some low-temperature evolution maxima. Diffusion coefficients are typical of a hopping process. The relationships between these thermodynamic and kinetic parameters are discussed.