Gate-Tunable Electrostatic Friction of Grain Boundary in Chemical-Vapor-Deposited MoS2

Two-dimensional (2D) semiconducting materials, such as MoS₂, are widely studied owing to their great potential in advanced electronic devices. However, MoS₂ films grown using chemical vapor deposition (CVD) exhibit lower-than-expected properties owing to numerous defects. Among them, grain boundary (GB) is a critical parameter that determines electrical and mechanical properties of MoS₂. Herein, we report the gate-tunable electrostatic friction of GBs in CVD-grown MoS₂. Using atomic force microscopy (AFM), we found that electrostatic friction of MoS₂ is generated by the Coulomb interaction between tip and carriers of MoS₂, which is associated with the local band structure of GBs. Therefore, electrostatic friction is enhanced by localized charge carrier distribution at GB, which is linearly related to the loading force of the tip. Our study shows a strong correlation between electrostatic friction and localized band structure in MoS₂ GB, providing a novel method for identifying and characterizing GBs of polycrystalline 2D materials.