Direct Visualization of Metal-Induced Gap State Distribution and Valley Band Evolution at Metal Versus Semimetal MoS₂ Interfaces

The interlayer coupling between metals and the two-dimensional (2D) semiconductors' conduction band (CB), encompassing metal-induced gap states (MIGS) and valley band modulation, critically influences both the Schottky barrier height (SBH) and intrinsic sheet resistance. Understanding the CB modulation induced by metals/semimetals is, therefore, essential for contact engineering optimization. Given that the MIGS decay length and orbital interactions are spatially confined to the nanoscale region proximate to the 2D semiconductor interface, we employed scanning tunneling microscopy/spectroscopy to quantitatively determine the MIGS decay length and CB minimum on various metal/semimetal substrates. This approach enabled the comprehensive characterization of MIGS distribution, charge neutrality level variation, and SBH properties. Our findings demonstrate that maintaining valley band structure integrity during semimetal interlayer coupling facilitates reduced intrinsic sheet resistance. These results elucidate the mechanism underlying weak interlayer coupling at semimetal-2D semiconductor junctions and their superior contact transport performance, providing insights into the rational design of future 2D-based devices.