Zeta-factor Determination Using Metal Thin Films for STEM-SDD Compositional Analysis of Iron-based Alloy Systems

The zeta (zeta) factor proposed by Watanabe and Williams [M. Watanabe and D. B. Williams, J. Microsc. 221, 89 (2006)] is a fundamental parameter for quantitative X-ray analysis with consideration of X-ray absorption using scanning transmission electron microscopy in combination with silicon drift detectors (STEM-SDD). In this study, the zeta-factors for Fe and Mn in iron-based alloy systems were determined by two thin-film approaches, namely, the "lift-off method" and the "direct deposition method". The Mn content in the Fe-Mn alloy obtained by using the zeta-factor, which was measured with Mn thin films directly deposited on a transmission electron microscopy (TEM) mesh grid, was in good agreement with the composition determined by fluorescent X-ray analysis. Determination of the accurate film thicknesses is essential for the accurate measurement of the zeta-factors. A layered structure and a directly deposited thin film is found effective for a standard sample to prevent bending and overlapping of samples. It is proved that the proposed method to fabricate the standard sample is useful for quantitative X-ray analysis with existing STEM-SDD system.