Epitaxial Synthesis of Molybdenum Carbide and Formation of a MoC/MoS Hybrid Structure via Chemical Conversion of Molybdenum Disulfide.

The epitaxial synthesis of molybdenum carbide (MoC, a 2D MXene material) via chemical conversion of molybdenum disulfide (MoS) with thermal annealing under CH and H is reported. The experimental results show that adjusting the thermal annealing period provides a fully converted metallic MoC from MoS and an atomically sharp metallic/semiconducting hybrid structure via partial conversion of the semiconducting 2D material. MoC/MoS 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 MoC grows and forms a MoC/MoS hybrid structure. The results show that MoC conversion is initiated at the MoS edge and undergoes sequential hydrodesulfurization and carbide conversion steps, and an atomically sharp interface with MoS forms through epitaxial growth of MoC. 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.