Contribution of the fluorescence to conversion electron yield X-ray absorption fine-structure measurements

Influence of an extra electron yield induced by the fluorescence process ha s been experimentally shown and analytically described. Analyse of the conv ersion electron yield (CEY) signal induced by pure bulk Ag (Ag K edge) and pure bulk Ni or Cu recovered by a thin Fe layer (Ni and Cu K edges) has bee n performed. This fluorescence electron yield leads to enhancement of the e dge height, modification of the shape of the X-ray absorption near-edge str ucture and decrease of the extended X-ray absorption fine-structure (EXAFS) amplitude. Extrapolation of the model concerning unrecovered bulk samples was carried out in order to explain the EXAFS amplitude reduction often obs erved in CEY measurements with respect to that obtained in the transmission mode. The reduction Delta chi/chi increases with increasing atomic number Z of the studied element. Delta chi/chi can be considered as negligible for low-Z elements (Ni and Cu). It becomes important for high-Z elements. The k dependence of the amplitude reduction is rather limited and this reductio n can be simply explained by a proportional factor. In order to correct thi s unwanted effect, a theoretical calculation process can be performed or th e sample structure can be specially designed to minimize it. Thin films dep osited on a substrate consisting of a low-Z element do not generate signifi cantly this extra electron yield.