Thermal Stability and Mechanical Properties of Cu-Nb Nanocomposite Thin Films

Nanostructured Cu-Nb thin films with composition ranging from Cu72Nb28 to Cu62Nb38 were prepared by hybrid modulated pulsed power magnetron sputtering and pulsed dc magnetron sputtering to study the thermal stability and mechanical properties. Through a vacuum annealing treatment from 200 to 400 & DEG;C, the structure and mechanical properties of Cu69Nb31 thin films are insensitive to the thermal changes, despite Cu-Nb are generally thermal unstable in kinetic Monte Carlo modeling with its initial decomposition temperature of about 200 & DEG;C. The hardness and modulus of Cu69Nb31 films showed a slight decrease from 7.2 to 6.6 GPa and 168.4 to 165.3 GPa pre and post annealing, and the films were believed to be thermal insensitive over 400 & DEG;C. The thermal stability of Cu-Nb nanocomposite thin films is enhanced by highly dispersed Nb-rich nanoprecipitates embedded in a Cu-rich phase, and the multiple interfaces brought by Nb-rich nanoprecipitates and Cu-rich phase reinforced the solute drag effect and Zener pinning should be responsible for the enhanced thermal stability of Cu-Nb nanocomposite thin films.