Evaluation of analysis volume in total reflection X-ray fluorescence analysis

Total reflection X-ray fluorescence (TXRF) is widely used for trace elemental analysis, wherein a thin monochromatic X-ray beam is typically applied at glancing angles. The actual volume of the sample measured by the instrument (analysis volume) depends on the dimensions of the X-ray beam and glancing angle, and it is a key feature in sample preparation for TXRF analysis. Herein, the analysis volume, including the analysis region and analysis height, was experimentally evaluated. A thin Au layer approximately 5 nm thick and 1 mm in diameter was prepared at a specific position on a flat glass substrate using a vacuum evaporation device. The position of this Au layer was controlled by manipulating a mask plate with a small hole. Nine samples were prepared at different Au layer positions and analyzed at 8 azimuth angles using a tabletop TXRF instrument. Finally, the Au XRF intensity distribution was visualized on a glass substrate. It was found that the XRF emitted over a diameter of approximately 5 mm was effectively detected using the tabletop TXRF instrument. The analysis height was experimentally evaluated using a thin Au layer deposited on a polyimide film 5 mm in diameter and 5 nm thick. The Au layer height was adjusted by inserting polyimide thin films between the Au layer and the glass substrate. The Au XRF intensity drastically decreased with increasing Au layer height, suggesting that the XRF emitted from the sample is effectively detected at heights of <10 mu m by using the described setup.