Positive charge-mediated phase modulation of MoTe2 synthesized by molecular beam epitaxy

Abstract

Polymorphic phase transition between semi-conducting 2H and semi-metallic 1T′ in MoTe2 has garnered significant interest due to its wide applicability for memory device. Recently, it has been reported that charge doping is a prospective method for facilitating practical application of phase transition. In particular, the positively doped system with lower energy barrier between two phases is more advantageous than the negatively doped system. However, although various methods for negative charge-mediated phase transition have been developed, study on positive charge-mediated phase transition is scarce due to the requirement of high charge density. Herein, we report positive charge-mediated phase modulation in MoTe2 synthesized by molecular beam epitaxy. The structural phase of MoTe2 is significantly influenced by the stoichiometric ratio of molybdenum to tellurium, and the tellurium adatoms make 1T' phase more stable than 2H phase. Photoelectron spectroscopy reveals that positive charge doping by electron transfer to tellurium adatoms is crucial in the determination of phase. Finally, based on the energy difference and energy barrier between two phases, the doping effects during and after synthesis are verified. This study on the structure modulation of MoTe2 provides physical insight for phase transition as well as a basis for the development of nanoscale electronic devices.