Radiation damage and spatial resolution in the EXELFS of inorganic materials

Abstract

EXELFS, the extended energy loss fine structure superimposed on the high energy loss side past an inner-shell electron excitation in an EELS spectrum, contains quantitative information about the local structure around the scattering atom from which the core electron is excited, similar to that contained in the x ray absorption fine structure (XAFS). Main advantages of the EXELFS technique over XAFS include the relative ease in the former to study the local environments of low Z elements coupled to the higher spatial resolution, imaging and diffraction capabilities of the TEM.Radiation damage to the sample caused by the energetic electron beam, however, has been an important concern to whether EXELFS can be safely applied to study materials at the nanometer scale. To investigate this question we chose to study Al, SiC and MgO as representatives of three different classes of binding: metallic, covalent and ionic, with the belief that these should exhibit different sensitivities to different mechanisms of radiation damage and hence will be fair representatives of a wide variety of materials.