Epitaxial Growth of Two-Dimensional Metal-Semiconductor Transition-Metal Dichalcogenide Vertical Stacks (VSe2/MX2) 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 (VSe2/MX2, M: Mo, W; X: S, Se) by a two-step chemical vapor deposition method. Intriguingly, the metallic VSe2 preferred to nucleate and extend from the energy-favorable edge site of the semiconducting MX2 underlayer to form VSe2/MX2 vertical heterostructures. This growth behavior was also confirmed by density functional theory calculations of the initial adsorption of VSe2 adatoms. In particular, the formation of Schottky-diode or Ohmic contact-type band alignments was detected for the stacks between VSe2 and p-type WSe2 or n-type MoSe2, 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.