Gate-Tunable Electrostatic Friction of Grain Boundary in Chemical-Vapor-Deposited MoS 2 .

Two-dimensional (2D) semiconducting materials, such as MoS 2 , are widely studied owing to their great potential in advanced electronic devices. However, MoS 2 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 MoS 2 . Herein, we report the gate-tunable electrostatic friction of GBs in CVD-grown MoS 2 . Using atomic force microscopy (AFM), we found that electrostatic friction of MoS 2 is generated by the Coulomb interaction between tip and carriers of MoS 2 , 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 MoS 2 GB, providing a novel method for identifying and characterizing GBs of polycrystalline 2D materials.