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

Abstract

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 VSe 2 , free from artificial factors. Here, we report high-quality octahedral 1T-VSe 2 single crystals grown by chemical vapor transport. Spectroscopic analyses identified that as-grown VSe 2 crystals were a single phase of VSe 2 and highly oriented along the (00l) plane. High-resolution scanning transmission electron microscopy verified that as-grown VSe 2 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 VSe 2 crystals to turn into largesized VSe 2 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.

Topological Phase and Quantum Anomalous Hall Effect in Ferromagnetic Transition-Metal Dichalcogenides Monolayer 1T−VSe2

“…Similar to other transition metal dichalcogenides in the phase, the transition metal atom, vanadium (V), locates at the center plane sandwiched between two chalcogen anions, selenium (Se). By adopting the experimental lattice constant 3.36 Å [ 14 , 30 ], the optimized V–Se bond length is 2.49 Å with the corresponding interlayer distance being 1.56 Å.…”

Ultrafast Interfacial Carrier Dynamics and Persistent Topological Surface States in VSe2/Bi2Se3 Van Der Waals Heterojunctions

“…Each Raman mode showed in good agreement with the previous studies of 1T-VSe2 and Bi2Se3. [43,44] Note that the absence of Raman mode of the semiconducting 2H-VSe2 at 190cm -1 , [45] which can be formed by structural phase transition during the preparation process, implies that the VSe2 used in this study was a pure metallic 1T-phase. The thicknesses of VSe2 at the marked positions (1, 2, 3, and 4) were measured to be 48, 74, 118, and 167 nm on 10 QL Bi2Se3 by atomic force microscopy (AFM), respectively (Fig.…”

“…A Bi2Se3/Al2O3 (001) film was grown at 250°C for 90 min, followed by a post-annealing process of Single crystalline 1T-VSe2 was grown by the chemical vapor transport method. [43] V (99.5% purity) and Se (99.999% purity) powders were used as the precursors with a stoichiometric amount of 2:1 wt%. As a transport agent (concentration of 1.5 mg/cm 3 ), VCl3 powder (99% purity) was used to provide sufficient vapor pressure.…”

Observation of pressure induced charge density wave order and eightfold structure in bulk VSe2

“…1 T -VSe 2 is stable under ambient condition 34 . Researchers have achieved great advances in the chemical vapor transport growth of high-quality and large-size 1T-VSe 2 single crystals 35 . Under high pressure, previous studies mainly focus on the pressure range of 0–30 GPa, and a first-order phase transition has been reported to occur at 15 GPa 36 .…”