The study of internal friction in nanocrystalline Ag and Au thin films

• Use of capacitance-based system to measure energy loss in ultra-thin Ag and Au films
• Strong film thickness dependence of internal friction in thin and ultrathin films
• Reduction of internal friction of Ag films by a factor of 3–28 upon annealing
• Film grain sizes and boundaries were controlled with respect to the dynamic properties.

This study investigated the internal friction in nanocrystalline silver and gold thin films (40–170 nm thick) deposited on silicon substrate. Paddle-like samples were designed to present uniform stress and all measurements were performed under high vacuum to eliminate the effects of air damping. Annealed thin films presented far less internal friction than as-deposited films. Annealing reduced the internal friction in Ag films by 3–28 times lower than those obtained from as-deposited films. Annealing reduced internal friction in Au films to 17%, 29%, and 42% in 41 nm, 90 nm, and 170 nm samples, respectively. With the exception of the thinnest Au film, the internal friction in all thin metal films was dependent on film thickness. In all cases, internal friction was affected by grain size and grain boundary.