Large-Area 2D Layered MoTe₂ by Physical Vapor Deposition and Solid-Phase Crystallization in a Tellurium-Free Atmosphere

Molybdenum ditelluride (MoTe₂) has attracted considerable interest for nanoelectronic, optoelectronic, spintronic, and valleytronic applications because of its modest band gap, high field-effect mobility, large spin–orbit-coupling splitting, and tunable 1T′/2H phases. However, synthesizing large-area, high-quality MoTe₂ remains challenging. The complicated design of gas-phase reactant transport and reaction for chemical vapor deposition or tellurization is nontrivial because of the weak bonding energy between Mo and Te. This study reports a new method for depositing MoTe₂ that entails using physical vapor deposition followed by a postannealing process in a Te-free atmosphere. Both Mo and Te are physically deposited onto the substrate by sputtering a MoTe₂ target. A composite SiO₂ capping layer is designed to prevent Te sublimation during the postannealing process. The postannealing process facilitates 1T′-to-2H phase transition and solid-phase crystallization, leading to the formation of high-crystallinity few-layer 2H-MoTe₂ with a field-effect mobility of ≈10 cm² V⁻¹ s⁻¹, the highest among all nonexfoliated 2H-MoTe₂ currently reported. Furthermore, 2H-MoS₂ and Td-WTe₂ can be deposited using similar methods. Requiring no transfer or chemical reaction of metal and chalcogen reactants in the gas phase, the proposed method is potentially a general yet simple approach for depositing a wide variety of large-area, high-quality, 2D layered structures.