Das Sweta, Mohapatra Niharika, Kumar Hemant
School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Odisha 752050, India.
J Phys Condens Matter. 2025 Jul 3;37(27). doi: 10.1088/1361-648X/ade756.
The nanoscale frictional properties of moiré superlattices in twisted MoSbilayers are governed by tip-sample interactions and the tunable moiré potential, modulated by twist angle (0°-6°) and strain, enabling tailored frictional responses. However, discrepancies between sharp-tip and larger-tip friction force microscopy measurements obscure lattice-scale dynamics, with theoretical models offering limited insight into tip-size and interlayer displacement effects on frictional amplitude. This study employs molecular dynamics simulations to probe the frictional behaviour of MoSbilayers across tip sizes (0.5-3 nm), revealing a transition from multiscale behaviour-lattice-scale stick-slip (0.32 nm) with sub-moiré amplitude modulation (0.15-1.2 nN)-to moiré-dominated periodicity (5-32 nm) as tip size increases. Larger tips average atomic-scale oscillations, shifting amplitude maxima from AB to AA stacking, a phenomenon driven by enhanced interlayer displacement. These findings resolve experimental inconsistencies, demonstrating lattice-scale periodicity's presence and its sub-moiré variation for the first time. This work provides insights into nanoscale tribological mechanisms in 2D materials, advocating high-resolution probes (<2 nm) for accurate frictional mapping and informing the design of moiré-based systems with engineered frictional properties.
扭曲的二硫化钼双层中莫尔超晶格的纳米级摩擦特性由针尖-样品相互作用和可调谐的莫尔势决定，该势由扭曲角（0°-6°）和应变调制，从而实现定制的摩擦响应。然而，尖锐针尖和较大针尖摩擦力显微镜测量之间的差异模糊了晶格尺度的动力学，理论模型对针尖尺寸和层间位移对摩擦振幅的影响提供的见解有限。本研究采用分子动力学模拟来探究不同针尖尺寸（0.5-3纳米）下二硫化钼双层的摩擦行为，结果表明，随着针尖尺寸增加，摩擦行为从多尺度行为——具有亚莫尔振幅调制（0.15-1.2纳牛）的晶格尺度粘滑（0.32纳米）——转变为以莫尔为主的周期性（5-32纳米）。较大的针尖使原子尺度的振荡平均化，将振幅最大值从AB堆叠转移到AA堆叠，这一现象由增强的层间位移驱动。这些发现解决了实验上的不一致性，首次证明了晶格尺度周期性的存在及其亚莫尔变化。这项工作为二维材料中的纳米级摩擦学机制提供了见解，提倡使用高分辨率探针（<2纳米）进行精确的摩擦映射，并为具有工程摩擦特性的基于莫尔的系统的设计提供了参考。
