Towards nanoscale EXELFS analysis: Limitation due to radiation damage

Spatial resolution limitations due to radiation damage were studied in the extended energy loss fine structure (EXELFS) spectroscopy technique using a transmission electron microscope (TEM). Three types of samples were used for testing that represented a wide variety of practical materials: a metal (Al) for metallic, a semiconductor (SiC) for covalent, and a ceramic (MgO) for ionic-bonding. A TEM was used that was operated under various experimental conditions, with emphasis in electron probe currents, for the EXELFS experiments. The radiation damage was monitored using the fine details of energy loss K-edge structures of various elements contained in the samples using the newly-developed AcqLong software for EXELFS acquisition and analysis. It was found that it is possible to obtain an EXELFS signal with excellent counting statistics allowing quantitative analysis of short range atomic order from local regions as small as 20-30 nm in Al, 3040 nm in SiC, and about 200 nm in MgO. Further improvements of spatial resolution toward nanoscale EXELFS analysis are discussed.