Authors: Watanabe¹; Ackland²; Williams²

Source: Journal of Microscopy, Volume 195, Number 1, 1 July 1999 , pp. 34-43(10)

Publisher: Wiley-Blackwell

Abstract:

Increasing the solid angle of X-ray collection is a major factor in improving the analytical sensitivity of X-ray energy-dispersive spectrometry (XEDS) in the analytical electron microscope (AEM). A new scanning transmission electron microscope, the VG HB 603, is equipped with two XEDS detectors with the largest collection angles (0.30 and 0.17 sr) available in commercial AEMs. However, large collection angles result in a large range of take-off angles, from ~ 4° to 36°, and the low angles can cause strong X-ray absorption. In order to investigate possible detrimental effects of the low (and of the range of) take-off angles on quantitative microanalysis of specimens exhibiting significant absorption, a stoichiometric Ni₃Al thin-film, in which the Al Kα line is significantly absorbed, was analysed. Furthermore, the effect of different values of the collection angle on X-ray intensities was theoretically evaluated by numerical calculations and spectral simulation. These theoretical approaches permitted correlation of changes in the X-ray take-off angle (and hence X-ray absorption) with changes in the collection angle. It is demonstrated that ~ 0.30 sr detectors, with minimum take-off angles as small as 4°, only result in maximum errors of 4% in the quantification of Al in Ni₃Al and, therefore, further increases in collection angle can be pursued while maintaining current levels of accuracy of quantification.

Keywords: Analytical electron microscopy; thickness determination; X-ray absorption; X-ray collection angle; X-ray take-off angle; ζ (zeta)-factor approach

Document Type: Research article

DOI: http://dx.doi.org/10.1046/j.1365-2818.1999.00481.x

Affiliations: 1: Research Laboratory for High Voltage Electron Microscopy, Kyushu University, Fukuoka 812-8581, Japan 2: Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015-3195, U.S.A.,

Publication date: 1999-07-01

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