Epitaxial Growth of Single-Phase 1T'-WSe2 Monolayer with Assistance of Enhanced Interface Interaction

The WSe2 monolayer in 1T' phase is reported to be a large-gap quantum spin Hall insulator, but is thermodynamically metastable and so far the fabricated samples have always been in the mixed phase of 1T' and 2H, which has become a bottleneck for further exploration and potential applications of the nontrivial topological properties. Based on first-principle calculations in this work, it is found that the 1T' phase could be more stable than 2H phase with enhanced interface interactions. Inspired by this discovery, SrTiO3 (100) is chosen as substrate and WSe2 monolayer is successfully grown in a 100% single 1T' phase using the molecular beam epitaxial method. Combining in situ scanning tunneling microscopy and angle-resolved photoemission spectroscopy measurements, it is found that the in-plane compressive strain in the interface drives the 1T'-WSe2 into a semimetallic phase. Besides providing a new material platform for topological states, the results show that the interface interaction is a new approach to control both the structure phase stability and the topological band structures of transition metal dichalcogenides.

Automated summary

Inspired by enhanced interface interactions, this study found that the 1T' phase of WSe2 may be more stable than the 2H phase. By growing WSe2 monolayers on SrTiO3 (100) substrate, a 100% single 1T' phase was achieved. In-plane compressive strain at the interface drove the 1T'-WSe2 into a semimetallic phase.