二维层状材料界面纳米摩擦行为的原子力显微探针操纵研究

Two-dimensional layered materials, offering unique atomic level flat interfaces and interlayer van der Waals forces, have been recognized as an ideal platform to study nanotribology behavior. Investigation on friction behavior at the interfaces of two-dimensional materials is of great significance to reveal the friction and lubrication mechanism and to solve the friction problem in microeletromechanical systems (MEMS). In this project, the interfacial friction behavior between layers will be investigated by manipulating the two-dimensional layered material MoS2 nanosheets with atomic force microscopy(AFM) tip, therefore solving the problem that most studies can only study the interface between the tip and one single material. By examining the influence of lattice commensurability, normal pressure, slip direction and other factors on the friction behavior at the interface of MoS2 Sheets, the difference in property and mechanism of the friction behavior between homogeneous interface and heterogeneous interface could be elaborated. By exploring the modulation principle of electric field on friction behavior, the regulation mechanism of interfacial charge/ potential on interfacial friction between MoS2 Sheets will be determined. By illustrating the relationship between interfacial friction behavior and electrical transport properties of MoS2 Sheets, a new way that can predict the frictional behavior through interfacial electrical transport properties can be proposed.

二维层状材料具有独特的原子级平整的界面及层间范德华力作用，成为研究纳米摩擦行为的理想体系。研究二维层状材料界面摩擦行为对于揭示摩擦和润滑机制以及微纳机电系统（MEMs/NEMs）中与运动相关的摩擦问题具有重要的意义。本项目通过原子力显微镜（AFM）针尖操纵二维层状材料MoS2纳米片进行滑移的方法，实现二维层状材料层间界面摩擦行为的研究，从而克服多数研究界面只能局限于针尖与单一材料表面的问题。通过测量MoS2层间界面相对滑移时的摩擦力，考察晶格公度性、正压力、滑移方向等因素对摩擦行为的影响规律，阐明二维层状材料同质界面与异质界面摩擦行为的不同及机理。探索利用外加电场调控MoS2层间界面摩擦力，确定界面电荷/电势对层间界面摩擦行为的调控机制。研究MoS2层间界面摩擦行为与层间电输运性质的关系，探讨利用层间电输运性质预测摩擦行为的新途径。

从原子/分子尺度研究摩擦现象对于理解摩擦力起源、解决微纳力学器件中的摩擦磨损问题具有重要意义。作为一种微纳尺度摩擦的研究手段，摩擦力显微技术受针尖材料单一、尖端原子结构和形态难以确认等问题的约束，难以研究两个相互摩擦表面的晶体结构、取向、接触面积和边缘等对摩擦力的影响。本项目围绕二维材料界面摩擦力测量及摩擦机制问题，发展了基于AFM针尖操纵的摩擦力测量技术，研究了二维范德华异质结构MoO3/石墨中的界面摩擦性质，取得了如下创新性成果： 1. 发展了基于AFM针尖操纵的摩擦力测量技术，建立了纳米结构单元可控操纵与界面摩擦力测量的研究方法。2. 采用范德华外延生长构筑了MoO3/石墨摩擦体系，研究了层间摩擦力与晶体相对转角、接触面积、边缘等的关系，为理解原子/分子尺度摩擦现象提供了实验证据。3. 研究了界面水插层对摩擦力的影响，提出了界面二维冰结构有序度变化带来的摩擦耗散。4. 发展了利用悬空纳米线校准AFM摩擦力的新方法，实现了摩擦力的精准定量测量。