ON THE STRUCTURAL-PROPERTIES OF A-SI1-XCX-H THIN-FILMS

The structural and chemical properties of hydrogenated amorphous silic on carbide (a-Si1-xCx:H) thin films, deposited by plasma-enhanced chem ical-vapor deposition, were determined by extended x-ray absorption fi ne structure (EXAFS), x-ray-absorption near-edge spectroscopy (XANES), small-angle x-ray scattering, Fourier transform infrared (FTIR) spect roscopy, Auger electron spectroscopy, and visible spectrometry. The EX AFS and XANES results show the crucial influence of the ''starving'' p lasma deposition conditions on the structural properties of wide-gap a -Si1-xCx:H films and are consistent with the FTIR and optical-absorpti on data. The first-neighbors distance for alloys with smaller carbon c ontent or deposited at higher silane flow are very close to the mean S i-Si distance obtained for a-Si:H. On the other hand, the EXAFS spectr a of films with higher carbon content (x>50 at. %) and deposited under ''starving'' plasma regime show Si-C distances similar to crystalline SiC (c-SiC). The presence of a typical c-SiC resonance in the XANES s pectra of the same samples is evidence that the material has a chemica l order close to that of c-SiC. (C) 1996 American Institute of Physics .