Influence of the deposition conditions on the optoelectronic properties of R.F. magnetron sputtered a-Si:H films

Abstract

We have studied the effect of the deposition conditions on the hydrogen incorporation modes and content and their effects on the optoelectronic properties of three different series of a-Si:H films prepared by R.F. magnetron sputtering at high substrate temperature (250 °C) and high deposition rates (~ 10 A/s). We have correlated infrared absorption measurements with optical transmission and Photothermal Deflection Spectroscopy (PDS) experiments. The samples were characterized successively in their as-deposited state and after annealing at a temperature around 180 °C. The results indicate that the modes of H incorporation as well as the hydrogen content in the three series are completely different from those observed for the samples prepared by Plasma Enhanced Chemical Vapour Decomposition of pure silane (P.E.C.V.D.) at the same substrate temperature. The microstructure of the films is also different. The density of deep defects measured in the as-deposited is slightly higher in the former case. This density decreases significantly after annealing at 180 °C and becomes comparable to that obtained for a-Si:H samples prepared by P.E.C.V.D. at 250 °C at low deposition rates (~ 1 A/s), with however a higher disorder in the R.F. sputtered films.