Direct characterizations of the two component surfaces of a solid-solid interface are essential for understanding its various interfacial mechanical, physical, and electrical behaviors. Particularly, the fascinating phenomenon termed structural superlubricity, a state of nearly zero friction and wear, is sensitively dependent on the interface structure. Here we report a controllable pick-and-flip technique to separate a microscale contact pair for the characterization of its two component surfaces for van der Waals layered materials. With this technique, the interface of a graphite superlubric contact is characterized with resolution from microscale down to the atomic level. Imaging of the graphite lattice provides direct proof that this superlubric interface consists of two monocrystalline surfaces incommensurate with each other. More importantly, the structure-property relationship for this contact is investigated. Friction measurements combined with fully atomistic molecular dynamics reveal that internal structures [internals steps, pits, and bulges buried underneath the topmost graphene sheet(s)] have negligible contribution to the total friction; in contrast, external defects lead to a high friction. These results help us to better understand the structure of highly oriented pyrolytic graphite and the fundamental mechanisms of structural superlubricity, as well as to guide the design of superlubricity-based devices.

中文翻译：

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微米级超润滑石墨界面的表征。

固-固界面的两个组成表面的直接表征对于理解其各种界面机械，物理和电气行为至关重要。特别是，被称为结构超润滑性（一种几乎零摩擦和磨损的状态）的迷人现象敏感地取决于界面结构。在这里，我们报告了一种可控的拾取和翻转技术，用于分离微型接触对，以表征范德华层状材料的两个组成表面。通过这种技术，石墨超润滑接触的界面具有从微米级到原子级的分辨率。石墨晶格的成像直接证明了这种超润滑界面由两个彼此不相称的单晶表面组成。更重要的是，研究该接触的结构-性质关系。摩擦测量与完全原子的分子动力学相结合，揭示出内部结构[埋在最顶层石墨烯片下面的内部台阶，凹坑和凸起]对总摩擦的贡献可忽略不计；相反，外部缺陷导致高摩擦。这些结果有助于我们更好地理解高度取向的热解石墨的结构以及结构超润滑性的基本机理，并指导基于超润滑性的器件的设计。埋在最顶层石墨烯片下面的凸起]对总摩擦的贡献可忽略不计；相反，外部缺陷导致高摩擦。这些结果有助于我们更好地理解高度取向的热解石墨的结构以及结构超润滑性的基本机理，并指导基于超润滑性的器件的设计。埋在最顶层石墨烯片下面的凸起]对总摩擦的贡献可忽略不计；相反，外部缺陷导致高摩擦。这些结果有助于我们更好地理解高度取向的热解石墨的结构以及结构超润滑性的基本机理，并指导基于超润滑性的器件的设计。