Electron-probe X-ray microanalysis of thin films

Abstract

The electron-probe x-ray microanalyser is normally used to study surfaces of thick specimens. A method is given here for the microanalysis of thin films. The film thickness is monitored by using the continuous x-ray spectrum. The ratio of the numbers of characteristic quanta to continuum quanta gives a measure of the concentration of an element in the film which is independent of the thickness of the film. The accuracy of the method is approximately 8% M.P.E. for films in the thickness range 0-0·5 mg cm−2.

Semiquantitative Chemical Analysis of Asbestos Fibers and Clay Minerals with an Analytical Electron Microscope

“…In the case of very thin specimens, as used for the transmission electron microscope, however, the analytical technique for bulk specimens cannot be employed simply. Several techniques have been developed primarily for the quantitative determination of elemental concentration in ultrathin specimens (Marshall and Hall, 1968;Namae, 1975;Chandler and Morton, 1976). Marshall and Hall (1968) showed the concentration of an element could be determined by the ratio of the intensity of the characteristic line to that of the continuous radiation from the same analyzing point.…”

“…Several techniques have been developed primarily for the quantitative determination of elemental concentration in ultrathin specimens (Marshall and Hall, 1968;Namae, 1975;Chandler and Morton, 1976). Marshall and Hall (1968) showed the concentration of an element could be determined by the ratio of the intensity of the characteristic line to that of the continuous radiation from the same analyzing point. The method proposed by Namae (1975) is simple and useful for a very thin specimen, without knowing the thickness of the specimens, when the constant K of an element is already determined.…”

“…The analytical electron microscope is capable of acquiring an X-ray spectrum from particles less than 200/~ in diameter in approximately 100 seconds. Marshall and Hall (1968) reported in their electron microprobe analysis of thin films that the concentration of an element can be obtained by measuring its characteristic X-ray intensity, and simultaneously, the intensity of a portion of the continuous X-ray spectrum. Consequently, the ratio of characteristic X-ray intensity to continuum X-ray intensity provides a measure of the concentration of an element which is independent of the thickness of the specimen.…”

“…The analytical techniques for bulk specimens are inapplicable to X-ray microanalysis of ultrathin specimens in the electron microscope, because the characteristic X-ray intensity depends on the thickness of the specimen as well as on the chemical composition. The effect of the specimen thickness on the characteristic X-ray intensity was eliminated by Marshall and Hall (1968). They showed that the intensity ratio of a characteristic peak to the intensity of the continuum provides a measure for the concentration of an element, which is independent of the film thickness.…”

Electron Probe Microanalysis

“…Marshall and Hall claim a 2% accuracy for colorimetric chemical weighing of thin films. (150) Interferometric measurements are not as reliable, since they only determine z, and thin films are not necessarily of bulk density.…”