Molecular Beam Epitaxy of Two-Dimensional Vanadium-Molybdenum Diselenide Alloys.
basic_science · Level V
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- Record sourced from PubMed, PMID 32794699.
- Also identified by DOI 10.1021/acsnano.0c02124.
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Abstract
Two-dimensional (2D) alloys represent a versatile platform that extends the properties of atomically thin transition-metal dichalcogenides. Here, using molecular beam epitaxy, we investigate the growth of 2D vanadium-molybdenum diselenide alloys, V<sub><i>x</i></sub>Mo<sub>1-<i>x</i></sub>Se<sub>2</sub>, on highly oriented pyrolytic graphite and unveil their structural, chemical, and electronic integrities <i>via</i> measurements by scanning tunneling microscopy/spectroscopy, synchrotron X-ray photoemission, and X-ray absorption spectroscopy (XAS). Essentially, we found a critical value of <i>x</i> = ∼0.44, below which phase separation occurs and above which a homogeneous metallic phase is favored. Another observation is an effective increase in the density of mirror twin boundaries of constituting MoSe<sub>2</sub> in the low V concentration regime (<i>x</i> ≤ 0.05). Density functional theory calculations support our experimental results on the thermal stability of 2D V<sub><i>x</i></sub>Mo<sub>1-<i>x</i></sub>Se<sub>2</sub> alloys and suggest an H phase of the homogeneous alloys with alternating parallel V and Mo strips randomly in-plane stacked. Element-specific XAS of the 2D alloys, which clearly indicates quenched atomic multiplets similar to the case of 2H-VSe<sub>2</sub>, provides strong evidence for the H phase of the 2D alloys. This work provides a comprehensive understanding of the thermal stability, chemical state, and electronic structure of 2D V<sub><i>x</i></sub>Mo<sub>1-<i>x</i></sub>Se<sub>2</sub> alloys, useful for the future design of 2D electronic devices.