The Critical Role of Interlayer Charge Transfer and Charge Redistribution Inducing the Formation of Phase-Pure Monolayer 1T'-MoTe.

1T'-MoTe exhibits a variety of intriguing physical properties, consisting of nontrivial higher-order topological behavior, ferroelectricity, superconductivity, and reversible phase transition. Hence, 1T'-MoTe has emerged as a hot spot in the fields of condensed matter physics and materials science. Nevertheless, the large-area synthesis of phase-pure 1T'-MoTe thin films has always been a big challenge for their widespread studies and device applications. In this study, three types of 1T'-MoTe/XTe heterojunction films are proposed and fabricated by molecular beam epitaxy. The mechanisms of lattice strain and charge transfer influencing the 2H-1T' phase transition are clearly elucidated, while centimeter-size and phase-pure monolayer 1T'-MoTe can be successfully fabricated via the choice of XTe functional layers. The results reveal that the substantial charge transfer of 0.005-0.056 e/f.u. at the heterojunction interface and the particular electron accumulation in Mo 4d orbitals (0.010-0.016 e/f.u.) are critical for the formation of 1T'-MoTe, while, in contrast, the effect from lattice strain that is induced by the underlying XTe layer is negligible. Owing to the most remarkable charge transfer effects, phase-pure monolayer 1T'-MoTe is achieved in the 1T'-MoTe/MnTe heterojunction film among all films. This study lays a solid foundation for the in-depth studies of the important physical properties and functional devices based on 1T'-MoTe films and provides valuable suggestions for effective phase control in similar materials utilizing heterojunction engineering.