Structural Analysis of Pd-Cu-Si Metallic Glassy Alloy Thin Films with Varying Glass Transition Temperature

Abstract

Thin films of Pd-Cu-Si metallic glassy alloys were fabricated by sputtering method, and the effect of the composition on glass transition temperature (T_g) was examined. In order to determine the mechanism of the observed effect, the structural parameters of the thin films based on the short-range order (SRO) were measured, and the correlations between the parameters and the composition were examined. The glass transition temperature (T_g) increased with increasing Si and Cu content. The atomic distances (Pd-Si and Pd-Pd) and the coordination number of Si atoms around a Pd atom (N_PdSi) increased with increasing Si content. The Pd-Pd atomic distance increased with increasing Cu content. These results suggest that Si content and Cu content have positive effect on the formation of a trigonal prism that is reported as a structural unit of Pd-based amorphous alloys. From these observed correlations, it can be concluded that T_g increases with an increase in the formation of a trigonal prism. Therefore, an increase in T_g with increasing Si and Cu content is supposed to be caused by the composition-dependent formation of trigonal prisms.