Diffusion and effusion analysis of hydrogen in undoped hydrogenated amorphous silicon thin films

Abstract

Device quality undoped a-Si:H thin films, were deposited by RF glow discharge onto silicon substrates and analyzed by thermal effusion spectroscopy and secondary ion mass spectrometry. The hydrogen effusion rate was simulated by applying the solution of the diffusion equations for a finite thickness film and hydrogen flow through the surface into a medium with zero concentration. The diffusion and effusion coefficients involved were determined from the depth profiles measured by SIMS after a number of heat treatments. Both coefficients were found to be dependent on the annealing time and the dispersion parameters were determined. The calculated hydrogen effusion rate was in good agreement with the experimental result.