Epitaxial Growth of Two-Dimensional Metal-Semiconductor Transition-Metal Dichalcogenide Vertical Stacks (VSe/MX) and Their Band Alignments.

Two-dimensional (2D) metal-semiconductor transition-metal dichalcogenide (TMDC) vertical heterostructures play a crucial role in device engineering and contact tuning fields, while their direct integration still challenging. Herein, a robust epitaxial growth method is designed to construct multiple lattice-matched 2D metal-semiconductor TMDC vertical stacks (VSe/MX, M: Mo, W; X: S, Se) by a two-step chemical vapor deposition method. Intriguingly, the metallic VSe preferred to nucleate and extend from the energy-favorable edge site of the semiconducting MX underlayer to form VSe/MX vertical heterostructures. This growth behavior was also confirmed by density functional theory calculations of the initial adsorption of VSe adatoms. In particular, the formation of Schottky-diode or Ohmic contact-type band alignments was detected for the stacks between VSe and p-type WSe or n-type MoSe, respectively. This work hereby provides insights into the direct integration, band-alignment engineering, and potential applications of such 2D metal-semiconductor stacks in next-generation electronics, optoelectronic devices, and energy-related fields.