EXELFS (Extended Electron Energy Loss Fine Structure) of Amorphous and Crystalline SiC

摘要

Extended Electron Energy Loss Fine Structure (EXELFS) is a technique which is sensitive to the local atomic environment surrounding atoms. The ability to perform EXELFS measurements with the use of an electron microscope enables one to study materials properties at high spatial resolution. Its use as a method to evaluate amorphous materials is especially noteworthy since EXELFS is sensitive to the structure and composition within near neighbor distances of specific types of atoms. The materials used in this study included single crystal SiC, single crystal SiC made amorphous by ion implantation with chromium, and single crystal SiC made amorphous under a converged 300 kV electron beam. EXELFS results, based upon the Si K edge, exhibit significant differences for crystalline SiC versus the SiC made amorphous by ion implantation. The position of peaks in the radial distribution function (RDF), representing the Si-C and the Si-Si interatomic bonds, indicate an expansion in the nearest neighbor distances for the ion implanted amorphous SiC. Also the Si-Si/Si-C peak intensity ratio for the amorphous material was significantly lower than that for crystalline SiC. These results imply that the tetrahedral (Si-C) bonds are retained to a greater degree than the longer Si-Si bonds. A loss in coordination of the Si-Si bond indicates that the unit cell has undergone substantial damage. (ERA citation 12:046726)