Take-off angle-dependent X-ray fluorescence analysis of thin films on acrylic substrate

Evaporated thin films of Au, Pb, Ni, Mn and Ti on acrylic substrates were analyzed by the take-off angle-dependent X-ray fluorescence method. A peak of the take-off-angle-dependent curve was observed in the take-off angle range below the zero angle besides the normal peak above the zero angle. We considered that this additional peak was produced by the optical interference between the transmitted X-rays and the reflected X-rays in the thin film, and was observed through the side wall of the acrylic substrate because the linear absorption coefficient of the fluorescent X-rays in the acrylic plate was small. By using these peaks, the zero angle was determined, and the density and thickness of the thin films were estimated by the fitting method.