Structural Study of a-Si1-xCx:H by EXAFS and X-ray Scattering

We present a comprehensive study of short range order in a-Si_1-xCx:H using X-ray scattering and Si K-edge EXAFS. The X-ray scattering probes the total radial distribution function; by detailed fitting in R-space we measure short range order parameters around C and Si for the first and second shell. The C-C distances in first and second shell indicate that both carbidic and graphitic configurations are present. The coordination numbers indicate that there is a tendency to chemical order; at high C concentrations there is evidence for chemical order with phase separation. The EXAFS measurements probe local order in the Si-C alloy phase; there is clear evidence that even this phase is chemically ordered.