Mechanical performance of co-deposited immiscible Cu–Ta thin films

Abstract

The immiscible alloy Cu–Ta has the potential for enhanced mechanical performance in applications as a functional coating. To establish baseline mechanical properties, four Cu–Ta films were co-sputtered at the temperatures 23, 400, 600, and 800 °C and tested with nanoindentation at strain rates 5 $$\times $$ × 10−3 s−1 to 10 s−1. Each film had a unique microstructure morphology. The hardness and elastic modulus of the four films were insensitive to strain rate changes. Instead, the measured properties were spatially dependent, particularly in the 600 and 800 °C films. In those two films, there is a bimodal deformation behavior due to Cu-agglomeration under protruding grains and planar Ta-rich regions. Increasing the indentation depth revealed shear band suppression which is related to a homogenous distribution of flow stresses for all four microstructure morphologies. Finally, the Cu–Ta hardness appeared to follow a rule-of-mixtures when compared to extrapolated data of Cu and Ta monolithic films.

Bamboo-like dual-phase nanostructured copper composite strengthened by amorphous boron framework

“…Previous simulation and experimental work investigated the effects of diffusion kinetics and deposition parameters on the phase separation and nanostructure of binary thin films. [31][32][33][34][35] We calculated the formation energy of Cu-B substitutional and interstitial state, and the results are all positive (Supplementary Fig. 7a), indicating that Cu-B solid-solution structures are unstable.…”