Comparative study of the structural properties of nanocrystalline Ge : H plasma deposited onto the cathode and the anode using high hydrogen dilutions

Nanocrystalline Ge:H thin films were deposited simultaneously on both elect rodes of a conventional capacitively coupled reactor for plasma enhanced ch emical vapor deposition using highly H-2 diluted GeH4 as the source gas. Th e structure of the films was investigated by Raman scattering and X-ray dif fraction as a function of substrate temperature, H-2 dilution, and r.f. pow er. The hydrogen concentrations and bonding configurations were determined by infrared absorption spectroscopy. For anodic deposition, the preferred c rystallographic orientation and film crystallinity depend rather strongly o n the deposition parameters. This dependence can be explained by changing s urface mobilities of adsorbed precursors due to changes in the hydrogen cov erage of the growing surface. Cathodic deposition is much less sensitive to variations in the deposition parameters. It generally results in films of high crystallinity with randomly oriented crystallizes. Some possible mecha nisms for these differences between anodic and cathodic deposition are disc ussed. (C) 1999 Elsevier Science S.A. All rights reserved.