Pang Haosheng, Li Minglin, Gao Chenghui, Lai Lianfeng, Zhuo Weirong
School of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350108, China.
Fujian Key Laboratory of Medical Instrumentation and Pharmaceutical Technology, Fuzhou University, Fuzhou 350108, China.
Nanomaterials (Basel). 2018 May 31;8(6):387. doi: 10.3390/nano8060387.
Lateral-force microscopy is a powerful tool to study the frictional properties of two-dimensional materials. However, few works distinctly reveal the correlation between the tip radius with the tip⁻sample distance and the frictional properties of the two-dimensional (2D) materials. We performed molecular-dynamics simulations to study the atomic-scale friction of a typical two-dimensional single-layer molybdenum disulfide (SLMoS₂). The effects of tip radius and tip⁻sample distance on the frictional properties were analyzed and discussed. The frictional force⁻sliding-distance curves show typical stick⁻slip behaviors, and the periodicity can be used to characterize the lattice constants of SLMoS₂. Sub-nanoscale stick-slip movements occur in one-lattice sliding periods along with only the armchair (AC) direction and only when the tip radius is smaller than 3 Å with 1.47 Å tip-sample distance. At the same tip⁻sample distance, a smaller tip can provide a more detailed characterization and higher-precision frictional properties of SLMoS₂. A larger tip is capable of providing comparative frictional properties of SLMoS₂ at a proper vertical tip⁻sample distance, compared with the small tip.
横向力显微镜是研究二维材料摩擦特性的有力工具。然而，很少有研究能清晰揭示针尖半径与针尖-样品间距和二维材料摩擦特性之间的关系。我们进行了分子动力学模拟，以研究典型二维单层二硫化钼（SLMoS₂）的原子尺度摩擦。分析并讨论了针尖半径和针尖-样品间距对摩擦特性的影响。摩擦力-滑动距离曲线呈现出典型的粘滑行为，其周期性可用于表征SLMoS₂的晶格常数。亚纳米级的粘滑运动仅在沿扶手椅（AC）方向的一个晶格滑动周期内出现，且仅当针尖半径小于3 Å且针尖-样品间距为1.47 Å时发生。在相同的针尖-样品间距下，较小的针尖能够提供更详细的表征以及更高精度的SLMoS₂摩擦特性。与小针尖相比，较大的针尖在适当的垂直针尖-样品间距下能够提供SLMoS₂的可比摩擦特性。
