EXELFS χ-data renormalization

Abstract

Extended Electron Energy Loss Fine Structure (EXELFS) spectroscopy is useful not only because it contains the same local atomic structure information as XAFS (X-ray Absorption Fine Structure), but also it has good low Z element sensitivity, up to nanoscale spatial resolution, and the capability of combining other high spatial resolution TEM measurements together with EXELFS. Until presently, due to poor quality of the EELS data, however, the EXELFS technique has not been developed to its full advantage. We have introduced various new methods to improve the data acquisition technique which includes removal of channel to channel gain variation and correction of dark-current background under real conditions; on-line aligning and accumulation, of virtually unlimited number of spectra while monitoring the thickness change (sample drift), radiation damage, electron beam energy drifts, and change in energy resolution during measurements. We have also developed a systematic data analysis procedure which utilizes the sophisticated UWXAFS data analysis software package after correction of the differences between EXELFS and XAFS data.