Department of Mechanical Engineering, McGill Institute for Advanced Materials, McGill University, Montréal, QC H3A 2K6, Canada.
Nanotechnology. 2012 Apr 20;23(15):155701. doi: 10.1088/0957-4484/23/15/155701. Epub 2012 Mar 22.
Energy dissipation by internal friction is a property of fundamental interest for probing the effects of scale on mechanical behavior in nanocrystalline metallic films and for guiding the use of these materials in the design of high-Q micro/nanomechanical resonators. This paper describes an experimental study to measure the effects of frequency, annealing and grain size on internal friction at room temperature in sputter-deposited nanocrystalline aluminum films with thicknesses ranging from 60 to 120 nm. Internal friction was measured using a single-crystal silicon microcantilever platform that calibrates dissipation against the fundamental limits of thermoelastic damping. Internal friction was a weak function of frequency, reducing only by a factor of two over three decades of frequency (70 Hz to 44 kHz). Annealing led to significant grain growth and the average grain size of 100 nm thick films increased from 90 to 390 nm after annealing for 1 h at 450 (∘)C. This increase in grain size was accompanied by a decrease in internal friction from 0.05 to 0.02. Taken together, these results suggest that grain-boundary sliding, characterized by a spectrum of relaxation times, contributes to internal friction in these films.
内耗是研究纳米晶金属薄膜中尺度效应对力学行为影响的基本特性，也是指导这些材料在高 Q 微/纳机械谐振器设计中应用的关键。本文描述了一项实验研究，用于测量溅射沉积的纳米晶铝薄膜在室温下的内耗，这些薄膜的厚度在 60nm 至 120nm 之间，频率、退火和晶粒尺寸对内耗的影响。内耗通过单晶硅微悬臂梁平台进行测量，该平台可根据热弹阻尼的基本极限来校准耗散。内耗与频率的关系较弱，在三个数量级的频率范围内（70Hz 至 44kHz）仅降低了两倍。退火导致晶粒显著长大，100nm 厚薄膜在 450°C 退火 1 小时后平均晶粒尺寸从 90nm 增加到 390nm。晶粒尺寸的增加伴随着内耗从 0.05 降低到 0.02。综合来看，这些结果表明，晶界滑移（其弛豫时间谱特征）对这些薄膜的内耗有贡献。
