Visualization of Local Conductance in Few-Layer MoS₂ during Nitridation Process

Two-dimensional (2D) materials have attracted significant interest due to their distinctive physical properties. The ability to measure local conductivity distribution with nanoscale spatial resolution while minimizing sample preparation through a noninvasive approach is essential for investigating these novel properties. Microwave impedance microscopy (MIM), a scanning probe technique that measures tip–sample admittance in a non-contact geometry at microwave frequencies, has emerged as a robust tool for this purpose. In this work, we employ MIM to perform quantitative conductivity imaging of few-layer MoS₂ during a nitridation process, which involves the conversion of semiconducting MoS₂ to metallic MoN. The evolution of local conductivity at intermediate steps of the reaction clearly shows that the reactivity of MoS₂ decreased with the decrease of the number of layers and is associated with the twisted structure. Our work vividly demonstrates the microscopic conductivity distribution at each stage of reaction, which is important for understanding physical properties and material chemistry of 2D materials.