Measurement of Thin Metal Layers. Fluorescent X-Ray Production by Radioisotope Sources

The use of radioactive isotopes for simple x-ray fluorescence spectroscopy, and in particular for the measurement of thin films, is not new. It is shown that the method can have fairly wide application to the measurement of thin films of many elements, and that there is a choice of the thickness range in which the method is sensitive. The potential flexibility of the method is partly in the fact that there are three different ways of applying it---by using K x-ray excitation, L x-ray excitation, and absorption of x-rays excited in the base metal---and partly in the different response that can be obtained by varying the radioactive source used. To illustrate these general points, measurements on chromium, tin, and copper plate are reported and discussed. Limitations of the method are also discussed. (auth)