Capturing and Editing Te-Deficient Phases in Two-Dimensional Molybdenum Telluride Compound.

Phase engineering of stoichiometric two-dimensional materials and their heterostructures remains a formidable challenge due to the thermodynamic stability disparity among the stoichiometric phases. Here, we report a dynamic-equilibrium approach (DEA) to access Te-deficient polymorphs in the Mo-Te system. By dynamically balancing tellurium vacancy generation and refilling, we drive selective phase transitions along divergent pathways. Starting from 1T'-MoTe2, we access three distinct Te-deficient phases: a novel van der Waals (vdW) Mo5Te8 with a high density of mirror-twin boundaries, a Chevrel-type nonlayered Mo3Te4, and a quasi-1D vdW Mo6Te6. These transitions proceed through Te-vacancy-initiated nucleation, followed by epitaxial templating at phase boundaries, which transforms the polycrystalline matrix into single-crystal phases. Sequentially modulating the Te chemical potential allows for the on-demand synthesis of atomically sharp heterostructures, demonstrating in situ phase editing. Moreover, we achieved wafer-scale synthesis of uniform Te-deficient phases (Mo5Te8, Mo6Te6) by depositing a Mo capping layer to precisely regulate Te vacancy concentrations across the entire substrate. This scalable control enables the fabrication of phase-controlled heterostructure device arrays, underscoring their potential for phase-programmable electronics. This work establishes a defect-mediated pathway to Te-deficient phases and heterostructures.