Analysis of Thin Surface Layers by Fe-57 Mössbauer Backscattering Spectrometry

Fe-57 Mössbauer spectra for extremely thin surface layers (600–3000 Å) were obtained by detecting internal conversion electrons emitted after resonant absorption. The sample was placed inside a proportional counter specifically designed for Mössbauer backscattering measurements. Helium-10% methane flowgas was used to detect the conversion electrons. It is estimated from the observed spectra that this technique can be used to obtain Mössbauer backscattering spectra for iron-containing surface layers 50–3000-Å thick. Backscattering spectra for thicker surface layers (0.2–0.5 mil) were obtained by merely changing to an argon-10% methane flow-gas mixture and counting the 6.3-keV internal conversion x rays rather than conversion electrons.