Liu Xin-Z, Ye Zhijiang, Dong Yalin, Egberts Philip, Carpick Robert W, Martini Ashlie
Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 220 South 33rd Street, Philadelphia, Pennsylvania 19104, USA.
School of Engineering, University of California Merced, 5200 North Lake Road, Merced, California 95343, USA.
Phys Rev Lett. 2015 Apr 10;114(14):146102. doi: 10.1103/PhysRevLett.114.146102. Epub 2015 Apr 6.
Atomic force microscopy (AFM) and atomistic simulations of atomic friction with silicon oxide tips sliding on Au(111) are conducted at overlapping speeds. Experimental data unambiguously reveal a stick-slip friction plateau above a critical scanning speed, in agreement with the thermally activated Prandtl-Tomlinson (PTT) model. However, friction in experiments is larger than in simulations. PTT energetic parameters for the two are comparable, with minor differences attributable to the contact area's influence on the barrier to slip. Recognizing that the attempt frequency may be determined by thermal vibrations of the larger AFM tip mass or instrument noise fully resolves the discrepancy. Thus, atomic stick-slip is well described by the PTT model if sources of slip-assisting energy are accounted for.
利用原子力显微镜（AFM）以及对氧化硅尖端在Au(111)上滑动的原子摩擦进行的原子模拟，在重叠速度下开展了相关研究。实验数据明确显示，在高于临界扫描速度时会出现粘滑摩擦平台，这与热激活的普朗特 - 汤姆林森（PTT）模型相符。然而，实验中的摩擦力大于模拟中的摩擦力。两者的PTT能量参数具有可比性，细微差异归因于接触面积对滑动势垒的影响。认识到尝试频率可能由较大的AFM尖端质量的热振动或仪器噪声决定，这完全解决了差异问题。因此，如果考虑到滑动辅助能量的来源，PTT模型就能很好地描述原子粘滑现象。
