Low temperature total electron yield EXAFS study of Co xAg 1− x granular alloys

Abstract

Total electron yield (TEY) Co K edge extended X-ray absorption fine structure (EXAFS) experiments have been performed at low temperature on as deposited and annealed Co x Ag 1− x granular alloys with Co volume concentrations x = 0.2 and 0.35. A new design for a total electron yield detector operating close to liquid nitrogen temperature has been tested with success at ESRF and used for the experiments reported here. A very interesting feature of this study concerns the evolution of the neighbourhood of the Co atoms in these alloys as a function of x and of the annealing temperature. For x = 0.2, at the as deposited stage, one observes clearly the presence of an important fraction of Co in the substitutional sites of the Ag f.c.c. matrix, in addition to Co agglomerates. For x = 0.35 the Co precipitation process seems more advanced compared to x = 0.2. From the evolution of the intensity of the different peaks of the radial distribution, one can follow the agglomeration process of Co in the Ag matrix.