Epitaxial Synthesis of Molybdenum Carbide and Formation of a Mo₂C/MoS₂ Hybrid Structure <i>via</i> Chemical Conversion of Molybdenum Disulfide

Abstract

The epitaxial synthesis of molybdenum carbide (Mo₂C, a 2D MXene material) via chemical conversion of molybdenum disulfide (MoS₂) with thermal annealing under CH₄ and H₂ is reported. The experimental results show that adjusting the thermal annealing period provides a fully converted metallic Mo₂C from MoS₂ and an atomically sharp metallic/semiconducting hybrid structure via partial conversion of the semiconducting 2D material. Mo₂C/MoS₂ hybrid junctions display a low contact resistance (1.2 kΩ·μm) and low Schottky barrier height (26 meV), indicating the material's potential utility as a critical hybrid structural building block in future device applications. Density functional theory calculations are used to model the mechanisms by which Mo₂C grows and forms a Mo₂C/MoS₂ hybrid structure. The results show that Mo₂C conversion is initiated at the MoS₂ edge and undergoes sequential hydrodesulfurization and carbide conversion steps, and an atomically sharp interface with MoS₂ forms through epitaxial growth of Mo₂C. This work provides the area-controllable synthesis of a manufacturable MXene from a transition metal dichalcogenide material and the formation of a metal/semiconductor junction structure. The present results will be of critical importance for future 2D heterojunction structures and functional device applications.