Special Topics and Other X-Ray Methods

5 SPECIAL TOPICS AND OTHER X-RAY METHODS Coating and Film-Thickness Determinations 

An important application of x-ray spectroscopy in the metallurgical industry is measuring the thickness of coatings or films. The thickness can be calculated by determining either the intensity 7g of the characteristic radiation emitted from the substrate (after being attenuated by the coating) or by measuring the intensity /j of 

A typical thickness gauge of this type will measure an area of 40 cm with a repeatability of 1%. The measurement ranges for tin and zinc gauges using different sources are given in Table 14.5. Errors due to changes in hardness, chemical composition, and thickness are less than 0.3%. 

One of the first important applications of x-rays to the measurement of the thickness of coatings was in the control of tin plate on steel, using attenuation of the Fe Ka line. The incident radiation may be either polychromatic or monochromatic (the latter makes isolation of the signal from background easier). However, it is essential that the primary radiation be of sufficient energy to excite the substrate. In the example of tin on steel, x-rays or y-rays in the 10 to 25 keV range will excite 

Energy Secondary y-rays y-rays Secondary y-rays 

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It is worth noticing that wide varieties of topics from such scientific fields as atomic physics, relativistic effects, photoelectron, X-ray and Auger processes, metal physics, chemical bonding affects, solid state chemistry and the others weis presented in the first workshop. This was perfectly astoimding because most calculating methods of the molecular orbitals have been applied only to specialized fields in which a researcher, who has proposed and formulated the calculating method, has been involved. 

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