Session EC17 - Scattering From Particles and Surfaces.
ORAL session, Monday morning, March 22
Room 263W, GWCC
The Radial Distribution Function (RDF) of pure amorphous silicon (a-Si) has been determined with a high degree of precision. Amorphous Si membranes of 10 \mum thickness were prepared by ion implantation and chemical etch. High energy x-ray diffraction measurements were performed to characterize annealed (600^\circC, 1hour) and as-implanted self-supporting a-Si membranes. In order to obtain high resolution atomic structural information, a large region of reciprocal space, up to Q = 55 Åwas covered. A reference measurement on c-Si powder was performed under similar experimental conditions, so as to determine a high resolution RDF of c-Si powder. Calculation of the first neighbor shell coordination (C_1) as a function of maximum Q indicates that measurement of S(Q) out to at least 40 Åis required to reliably determine the RDF. A 2% change in C_1 and subtle changes in the rest of the RDF were observed upon annealing, consistent with point defect removal. After annealing, C_1 = 3.88, which would explain why a-Si is less dense than c-Si.
Work at Houston was supported by the DOE/BES on DE-FG05-8745325.