The total reflection x-ray fluorescence (TXRF) method is a powerful tool for the surface analysis of flat materials, such as Si wafers. The probing depth of TXRF is an important factor in a quantitative TXRF analysis. This is the first time that the probing depth under total-reflection conditions was experimentally evaluated by analyzing the takeoff-angle dependence of x-ray fluorescence. Our experimental results, measuring different incident angles, fit the theoretical curves. Finally, the relationship between the probing depth and the incident angle was obtained. We found the takeoff-angle dependent measurement of x-ray fluorescence to be a powerful means for determining the probing depth in the TXRF method.
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