EXELFS analysis of amorphous and crystalline silicon carbide

Abstract

SUMMARYCore‐shell ionization edges from thin specimens of cubic silicon carbide (c‐SiC) are studied by means of electron energy‐loss spectroscopy (EELS) in a transmission electron microscope (TEM). Special attention is paid to the investigation of extended energy‐loss fine structures (EXELFS) to study local order effects around silicon atoms as a function of disorder in SiC.Two forms of SiC were used: c‐SiC for the crystalline form, and friction‐induced amorphous silicon carbide (a‐SiC) for the disordered form.EXELFS are generated by the elastic backscattering of outgoing electron waves by neighbouring atoms. Results show that both Si‐K and Si‐L edges contain structural information. EXELFS at the Si‐K edge can be used to calculate the radial distribution function (RDF) in the same way as extended X‐ray absorption fine structures (EXAFS). EXELFS at the Si‐L edge can be isolated by digital filtering. The high signal‐to‐noise ratio at the Si‐L edge permits the effect of larger interatomic distances to be observed, and thus the EXELFS technique is of promise for studying the effect of disorder in Si‐based ceramic materials with a high spatial resolution (nanometre scale).