High quality factor metallic glass cantilevers with tunable mechanical properties

The resonant properties of bulk metallic glass (BMG) microcantilevers were studied. Pt57.5Cu14.7Ni5.3P22.5 BMG was used to fabricate the cantilevers, on the wafer scale, using a thermoplastic forming technique. The resonant behaviors of the cantilevers were then measured in air and various vacuum levels and annealing conditions. The quality factors increase predictably after annealing at temperatures below the glass transition temperature (Tg) for different times. The increase of quality factor of annealed cantilevers is attributable to the decrease in internal friction of the BMG due to thermally activated structural relaxation. Annealing above Tg resets the quality factor to values comparable to that of the as-formed cantilever. Therefore, the quality factor and mechanical properties of a cantilever could be tuned by the selection of suitable annealing temperatures and times. The measured quality factors are in excess of 2000 in air and 8100 in vacuum.