Dispersive and Nondispersive X-Ray Fluorescence Methods for the Measurement of the Thicknesses of Films of Cadmium Sulfide and Other II-VI Compounds
Cadmium sulfide and other II-VI compounds have been deposited on various substrates by the vacuum technique using a setup consisting of a mechanical pump and a diffusion pump. Attempts are being made to employ a high-speed turbo-molecular pump to produce the necessary vacuum. Such pumps have been claimed to produce higher vacuum than those of earlier types. The use of x-ray fluorescence seems to be the best method for the determination of thicknesses of films of these compounds. By using this method the determination can be carried out both rapidly and nondestructively, so that the samples can be used for further experimentation or preserved for future reference. Both the vacuum and air-path spectrometers were employed with the dispersive (conventional) x-ray fluorescence method, depending on the x-ray spectra used and the film thickness to be determined. The vacuum spectrometer described earlier has been modified to improve the intensity of the secondary x-ray. The modified setup with low-Z kit has been changed to accommodate four analyzing crystals in the vacuum chamber. The radioisotopes dysprosium-159, iodine-125, and others were used with the nondispersive x-ray fluorescence method. Recent instruments based on the dispersive and nondispersive systems are described here. Some of these instruments have been used to measure the thicknesses of films of II-VI compounds.
KeywordsScintillation Counter Cadmium Sulfide Analyze Crystal Cadmium Selenide Total Counting Time
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