Imaging the Thickness‐Dependent Formation of Schottky Barriers in Metal–Semiconductor van der Waals Heterostructures

Achieving high‐performance optoelectronic devices based on two‐dimensional van der Waals (vdW) heterostructures relies critically on the precise control of interfacial properties, in particular the formation and modulation of Schottky barriers. However, direct operando imaging of the energy landscape at these interfaces, which is critical for rational device design, remains highly challenging. Here, we employ nanoscale scanning x‐ray photoemission microscopy to visualize the spatial distribution of electric fields and band alignment within a model 2H‐TaS 2 (metal)/2H‐MoSe 2 (semiconductor) vdW heterostructure under applied bias. By tracking core‐level binding energy shifts with 700 nm spatial resolution, we reveal the accumulation of electric fields at both 3D metal–2D semiconductor and 2D metal–2D semiconductor interfaces, indicative of a Schottky barrier whose height depends on the flake thickness. Bulk‐like MoSe 2 exhibits negligible interfacial resistance, whereas a barrier (≈0.75 eV) emerges for the quantum‐confined form of the flake. These findings provide a direct visualization of charge injection pathways and underscore the role of quantum confinement in tuning barrier heights, offering a roadmap for engineering contacts in vdW‐based devices.