Structural coherence between phases in Ni0.35Ag0.65 thin films

Abstract

Ni0.35Ag0.65 thin films were studied by means of both x-ray absorption spectroscopy and x-ray diffraction, in the as-deposited and annealed states. Short-range-order investigation has established that nickel atoms are either clustered in small pure Ni aggregates or dispersed in an Ag-rich solid solution. For the as-deposited and 250 °C annealed samples, an accurate interpretation of the diffraction spectra requires one to take into account a degree of structural coherence between these two phases, which are preferentially oriented with the dense planes parallel to the surface. Local order and long-range-order characterizations then give coherent results. The mean size of the pure Ni aggregates increases from approximately 1 nm in the as-deposited state to 3-5 nm after a 400 °C anneal. The maximum Ni solubility in the Ag matrix was estimated to be around 7 at.% for these samples. All of the reported results - the natures of the various phases, and mean sizes, shapes and orientations of the aggregates - are discussed with regard to the other structural (extended x-ray absorption fine-structure, anomalous small-angle x-ray scattering) and magnetic information.