ROLE OF HYDROGEN SURFACE COVERAGE DURING ANODIC PLASMA DEPOSITION OF HYDROGENATED NANOCRYSTALLINE GERMANIUM

Nanocrystalline Ge:H films were deposited on the anode of a convention al plasma-enhanced chemical vapor deposition system using highly H-2-d iluted GeH4 as source gas. The structural changes with substrate tempe rature, hydrogen dilution, and rf power were investigated by x-ray dif fraction and Raman scattering. The hydrogen content and Il bonding con figuration were determined by infrared absorption spectroscopy. It was found that increased rf power mainly favors nucleation of grains whil e increased H-2 dilution mainly favors the subsequent growth of grains . Transitions from an amorphous to a crystalline and then back to an a morphous phase are observed as the substrate temperature is increased. The amorphous phase at high temperatures and variations in the prefer red crystallite orientations are explained by changes in the diffusion length of adsorbed precursors due to changing hydrogen coverage on th e growing surface. (C) 1998 American Institute of Physics.