Plasma and surface chemistry effects during high rate deposition of hydrogenated amorphous silicon

The plasma chemistry of an expanding thermal plasma in argon/hydrogen mixtu res in interaction with silane is discussed. Based on Langmuir probe measur ements and (appearance potential) mass spectrometry, it is argued that unde r optimal conditions in terms of the a-Si:H deposited the fluxes reaching t he growing film mainly consist of SiH3 and atomic hydrogen. The surface che mistry, hydrogen incorporation, growth rate and dependence on substrate tem perature are discussed and the results obtained are compared with growth mo dels as proposed by Matsuda, Gallagher and Perrin. It is argued that althou gh atomic hydrogen plays no role in the modification of the bulk properties , atomic hydrogen is probably responsible for the creation of dangling bond sites by hydrogen abstraction. Possible consequences for the substrate tem perature dependence of the growth rate are discussed.