Thermal stability of grain structure for Ag nanotwinned films sputtered with substrate bias

In this study, different grain growth paths after aging at various temperatures for 1 h were observed in Ag nanotwinned thin films with and without substrate bias voltage, which led to large differences in thermal stability. As-deposited Ag nanotwinned thin films with and without substrate bias voltage were characterized by FIB, EBSD, and TEM, which revealed thinner equiaxial fine-grained regions, higher amounts of (111)-oriented grains and denser nanotwin stacking perpendicular to the growth direction of columnar grains in thin films with -150 V substrate bias voltage. Due to the better lattice arrangement and densification of the crystal structure due to substrate bias voltage, the microstructures remained almost unchanged, except for a little equiaxial grain growth, even after aging at 450 °C for 1 h. However, in the Ag nanotwinned thin film without substrate bias voltage, severe abnormal grain growth (AGG) occurred after aging at only 250 °C for 1 h. Better understanding of the differences in thermal stability in nanotwinned thin films is provided in this study, and the findings will be beneficial for experimental design for further applications.