Phase transition and in situ construction of lateral heterostructure of 2D superconducting α/β Mo2C with sharp interface by electron beam irradiation

Lateral heterostructures of 2D materials have several interesting properties and potential applications, and they are usually fabricated by chemical vapor deposition. However, it still remains a great challenge to fabricate 2D lateral heterostructures with well-controlled patterns and sharp interfaces. Herein, we found that the 2D alpha-Mo2C crystal, a recently emerging 2D superconductor, experiences a phase transition from the alpha phase to beta phase on electron beam irradiation in a transmission electron microscope because of the migration of carbon atoms among the molybdenum octahedrons. Combined with first-principles calculations, the carbon atom migration paths and the corresponding energy barriers were discussed. Utilizing this unique phase transition property of 2D alpha-Mo2C crystal, we demonstrated the precise in situ construction of the lateral heterostructure of 2D superconducting alpha/beta Mo2C with a well-controlled pattern and sharp interface using advanced aberration-corrected scanning transmission electron microscopy.