Point Analysis in STEM
In STEM, an electron beam is scanned over a defined area of the sample. The beam can be localized on a certain point in the image and used to measure an EDX and/or EEL spectrum there. Moreover, line scans and mappings can be obtained by this powerful technique.
Metal nanoparticles dispersed on titanaia are recognizable in the Z-contrast image as bright patches. To solve the question whether the metal particles consist of an AuPd alloy or of separated Au and Pd nanoparticles, EDXS spot analyses were performed. EDX spectra obtained at the positions marked in the HAADF-STEM image show the characteristic signals of both metals - even for ca. 1 nm nanoparticles (point 2) - and thus prove the presence of an alloy.
Characterization of AuPd Nanoparticles by Probe-Corrected Scanning Transmission Electron Microscopy and X-Ray Absorption Spectroscopy
F. Krumeich, S. Marx, A. Baiker, R. Nesper, Z. anorg. allg. Chem. 637 (2011) 875-881 DOI