期刊
ULTRAMICROSCOPY
卷 193, 期 -, 页码 111-117出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ultramic.2018.06.013
关键词
STEM; Catalyst analysis; Adatom motion; Energy-dispersive X-ray spectrometry; Electron energy-loss spectroscopy
类别
资金
- Natural Sciences and Engineering Research Council of Canada
- NSF [DMR-0804528, DMR-1040229]
Fitted with a field emission source, aberration-corrected optics and an energy-dispersive X-ray detector of large solid angle, a modern analytical TEM can generate a current density high enough to chemically identify a single metal atom within a fraction of a second, if the atom remains stationary within the electron probe. However, atom motion will occur if the atomic binding energy is too low, the specimen temperature too high, or the electron accelerating voltage above a certain threshold. We discuss such motion in terms of thermal diffusion, beam-induced sputtering and beam-assisted surface migration. Calculations based on a Rutherford-scattering approximation suggest that when atomic displacement is possible, it drastically reduces the analytical signal and signal/noise ratio. For certain elements, electron energy-loss spectroscopy (EELS) provides a higher delectability than energy-dispersive X-ray (EDX) but suffers from the same problem of atomic displacement.
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