The measurement of atomic number and composition in an SEM using backscattered detectors

SUMMARY The atomic number dependence of electron backscattering can be used as the basis of a microanalysis technique. The operating procedures and condition for quantitative measurements of specimen atomic number are outlined and an expression relating the accuracy of composition to the atomic number sensitivity has been derived. Some measurements of the spatial resolution of backscattered electron microanalysis are also presented and compared with the resolution of X-ray microanalysis. Although the range of application of this technique is limited, where it can be applied it has the following advantages: (i) higher spatial resolution than X-ray microanalysis for bulk specimens; (ii) very rapid measurement; (iii) can be applied to compounds of low atomic number elements, (e.g. borides, carbides, nitrides, etc.); (iv) specimen preparation is often relatively straightforward.