Room-temperature diffusion-induced grain boundary migration in the fine-grained Pd side of CuPd diffusion couples

Abstract

Transmission election microscopy (TEM) and Auger electron spectroscopy (AES) were used to study interdiffusion between fine-grained (≈150 A ̊ ) Pd films and Cu substrates. TEM demonstrated that a fine-grained alloy having a constant composition (65% CuPd) is formed at room temperature in the Pd side of the couple. Furthermore, the alloy grains are epitaxial to Pd grains at the interface region. The alloy phase is formed by the so-called diffusion-induced grain boundary (GB) migration. The diffusion of Cu atoms into Pd grain boundaries causes the epitaxial nucleation of the alloy phase on the side of the Pd GBs. The alloy phase then grows into the other face, while maintaining the high diffusive nature of the original GBs. The estimated size of the alloy phase was in good agreement with published GB diffusivity data for the diffusion of Cu into Pd GBs.