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 (Tg) 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 (Tg) 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 (NPdSi) 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 Tg increases with an increase in the formation of a trigonal prism. Therefore, an increase in Tg with increasing Si and Cu content is supposed to be caused by the composition-dependent formation of trigonal prisms.