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 f or 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 experimen tal conditions, with emphasis in electron probe currents, for the EXELFS ex periments. The radiation damage was monitored using the fine details of ene rgy loss K-edge structures of various elements contained in the samples usi ng the newly-developed AcqLong software for EXELFS acquisition and analysis . It was found that it is possible to obtain an EXELFS signal with excellen t counting statistics allowing quantitative analysis of short range atomic order from local regions as small as 20-30 nm in Al, 30-40 nm in SIG, and a bout 200 nm in MgO. Further improvements of spatial resolution toward nanos cale EXELFS analysis are discussed. (C) 1999 Elsevier Science Ltd. All righ ts reserved.