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Determination of the band parameters of bulk 2H-MX₂ (M = Mo, W; X = S, Se) by angle-resolved photoemission spectroscopy.

ABSTRACT: Monolayer MX₂ (M = Mo, W; X = S, Se) has recently been drawn much attention due to their application possibility as well as the novel valley physics. On the other hand, it is also important to understand the electronic structures of bulk MX₂ for material applications since it is very challenging to grow large size uniform and sustainable monolayer MX₂. We performed angle-resolved photoemission spectroscopy and tight binding calculations to investigate the electronic structures of bulk 2H-MX₂. We could extract all the important electronic band parameters for bulk 2H-MX₂, including the band gap, direct band gap size at K (-K) point and spin splitting size. Upon comparing the parameters for bulk 2H-MX₂ (our work) with mono- and multi-layer MX₂ (published), we found that stacked layers, substrates for thin films, and carrier concentration significantly affect the parameters, especially the band gap size. The origin of such effect is discussed in terms of the screening effect.

SUBMITTER: Kim BS

PROVIDER: S-EPMC5090988 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Determination of the band parameters of bulk 2H-MX2 (M = Mo, W; X = S, Se) by angle-resolved photoemission spectroscopy.

Kim Beom Seo BS Rhim Jun-Won JW Kim Beomyoung B Kim Changyoung C Park Seung Ryong SR

Scientific reports 20161102

Monolayer MX2 (M = Mo, W; X = S, Se) has recently been drawn much attention due to their application possibility as well as the novel valley physics. On the other hand, it is also important to understand the electronic structures of bulk MX2 for material applications since it is very challenging to grow large size uniform and sustainable monolayer MX2. We performed angle-resolved photoemission spectroscopy and tight binding calculations to investigate the electro ...[more]

PMID: 27805019

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Project description:Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are new crystalline materials with exotic electronic, mechanical, and optical properties. Due to their inherent exceptional mechanical strength, these 2D materials provide us the best platform for strain engineering. In this study, we have performed first-principles calculations to study the effect of uniaxial strains on the electronic, magnetic, and mechanical properties of transition-metal dichalcogenides (TMDs) MX2 (where M = Cr, Mo, W and X = S, Se), monolayers (2D), and armchair and zigzag nanoribbons (1D). For the mechanical strength, we determined the tensile strength (σ) and Young's modulus (Y) and observed that σ and Y are higher in monolayers (most in WS2ML) as compared to nanoribbons where monolayers resist tension up to 25-28% strain while nanoribbons (armchair and zigzag) can be only up to 5-10%. Deformation potential (Δ p ) in the linear regime near the equilibrium position(ϵ < 2%) has also been calculated, and its effect on monolayers is observed less as compared to nanoribbons. In addition, unstrained nonmagnetic monolayers are direct band gap semiconductors (D) which changed to indirect band gap semiconductors (I) with the application of strain. Ferromagnetic states of metallic zigzag nanoribbons (including up spin channel of 7-CrS2NR and 7-CrSe2NR) are greatly affected by strain and show half-metal-like behavior in different strain range. The magnetic moment (μ) that is predominantly observed in zigzag nanoribbons is 2 times higher than that of other nanoribbons. This magnetism in nanoribbons is mostly caused by transition-metal atoms (M = Cr, Mo, W). Thus, our study suggests that strain engineering is the best approach to modify or control the structural, electronic, magnetic, and mechanical properties of the TMD monolayer and nanoribbons which, therefore, open their potential applications in spintronics, photovoltaic cells, and tunneling field-effect transistors.

Dataset Information

Determination of the band parameters of bulk 2H-MX₂ (M = Mo, W; X = S, Se) by angle-resolved photoemission spectroscopy.

Publications

Determination of the band parameters of bulk 2H-MX<sub>2</sub> (M = Mo, W; X = S, Se) by angle-resolved photoemission spectroscopy.

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