In-Depth Structural Characterization of 1T-VSe2 Single Crystals Grown by Chemical Vapor Transport

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been extensively studied. Among them, vanadium dichalcogenides, a unique metallic family of the TMDCs, have been considered as potential room temperature ferromagnetic materials at the monolayer scale. However, further progress has been hampered by the difficulties growing monolayer and the challenges making high-quality single crystalline VSe2, free from artificial factors. Here, we report high-quality octahedral 1T-VSe2 single crystals grown by chemical vapor transport. Spectroscopic analyses identified that as-grown VSe2 crystals were a single phase of VSe2 and highly oriented along the (001) plane. High-resolution scanning transmission electron microscopy verified that as-grown VSe2 crystals not only had single crystalline nature, the octahedral 1T phase, and AAA stacking order in atomistic real space, but also supported valuable lattice information that differed from the predicted values of the previous calculation model. Mechanical exfoliation allowed our VSe2 crystals to turn into large-sized VSe2 flakes with various thicknesses. With in-depth structural analyses, our findings provide insight into further research of the fundamental calculation model and the crystallographic tailoring for intrinsic room-temperature 2D ferromagnetic materials.