Microstructural evolution of thin polycrystalline metallic films under extreme conditions

Abstract

Thin films are materials systems that are widely used in applications ranging from electronics and optical devices to industrial and biomedical ones. However, these systems are unstable against various homogenization processes and aging mechanisms (grain growth, coarsening, surface evolution, and diffusion of species) even at low service temperatures. In this work, we examine the role of various aspects of microstructure (grain boundary types and characters, free surfaces, surface diffusion, and thermal grooves) on the thermal aging of such systems. Existing experimental tools will be leveraged to characterize thin films, i.e., in-situ quantitative thermal annealing, and provide direct comparisons to predications emerging from a recently developed meso-scale model via Precession Electron Diffraction (PED). Parametric studies will be conducted to gain insights on the role of each of the aforementioned aspects of microstructure on the dynamics. Herein, we will focus on “hard” gold thin films (with alloying elements like Co, Ni, or Fe) as they are materials of choice in a wide range of applications at Sandia. Initially, pure gold systems are examined and future studies will focus on microstructure evolution in the presence of alloying elements and second-phase particles.