Development of EXELFS for nanoscale atomic structure determination

EXELFS spectroscopy contains the same local atomic structural information as XAFS; furthermore, it is readily applied to low Z elements, has high spatial resolution, and the capacity of combining other local TEM measurements. Due to hitherto relatively poor quality of the EELS data, the EXELFS technique has not been developed to its full advantage until recently. We introduced various new methods to improve the data acquisition including real-time alignment and accumulation of virtually unlimited number of spectra while monitoring sample drift, radiation damage, and changes in energy resolution. We also developed a systematic data analysis procedure which corrects for the differences between EXELFS and XAFS, and adopts the UWXAFS data analysis software package to perform EXELFS data analysis with the same level of sophistication. The technique is demonstrated for SiC.