The enhanced strength and electrical conductivity in Ag/Cu multilayers by annealing process

Abstract In this work, the hardness, electrical resistivity and thermal stability of annealed Ag/Nb multilayers were investigated with individual layer thickness (h) ranging from 3 to 100 nm after annealing at 200–400 °C. For all scales multilayers, the hardness improves 6–16% whereas the electrical resistivity decreases 6–12% after annealing at 200 °C compared with those of as deposited state. At 300 °C, the enhancement shows layer thickness dependent due to the different interfacial structures. The hardness improves about 4–10% and the electrical resistivity decreases 11–28% for multilayers with h ≥ 10 nm. A good combination of high strength and high conductivity has been obtained in annealed Ag/Cu multilayer with h ≥ 10 nm when annealing temperature is not more than 300 °C. Both hardness and electrical conductivity are enhanced by annealing process. The improvement of electrical conductivity mainly comes from the reduction of grain boundaries due to the grain growth. The enhancement of hardness relates with the increment of twin boundaries, the compressive stress and the lack of dislocations after annealing process.