Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers
School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China. Physical Chemistry Chemical Physics
(Impact Factor: 4.49).
09/2011; 13(34):15546-53. DOI: 10.1039/c1cp21159e
Very recently, two-dimensional nanosheets of MoSe(2), MoTe(2) and WS(2) were successfully synthesized experimentally [Science, 2011, 331, 568]. In the present work, the electronic and magnetic properties of perfect, vacancy-doped, and nonmetal element (H, B, C, N, O, and F) adsorbed MoSe(2), MoTe(2) and WS(2) monolayers are systematically investigated by means of first-principles calculations to give a detailed understanding of these materials. It is found that: (1) MoSe(2), MoTe(2) and WS(2) exhibit surprising confinement-induced indirect-direct-gap crossover; (2) among all the neutral native vacancies of MoSe(2), MoTe(2) and WS(2) monolayers, only the Mo vacancy in MoSe(2) can induce spin-polarization and long-range antiferromagnetic coupling; (3) adsorption of nonmetal elements on the surface of MoSe(2), MoTe(2) and WS(2) nanosheets can induce a local magnetic moment; H-absorbed WS(2), MoSe(2), and MoTe(2) monolayers and F-adsorbed WS(2) and MoSe(2) monolayers show long-range antiferromagnetic coupling between local moments even when their distance is as long as ∼12 Å. These findings are a useful addition to the experimental studies of these new synthesized two-dimensional nanosheets, and suggest a new route to facilitate the design of spintronic devices for complementing graphene. Further experimental studies are expected to confirm the attractive predictions.
Available from: Daniele Nuvoli
- "Analogously to graphite, the atoms in the layer are bound by strong covalent forces, while van der Waals interactions hold the layers together. In this context, monolayers of MoS 2 and WS 2 have received great attention because they are 2D semiconductor with tunable band gaps depending on size   . In particular, exfoliated WS 2 (EWS 2 ) was found to exhibit novel and superior properties with respect to the bulk structure, and hence such a nanomaterial has been used for the fabrication of catalysts , lubricants , lithium batteries , photoconductors , probes for scanning probe microscopy , shock absorbers , solar cell films . "
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ABSTRACT: For the first time, ultrasonication was exploited for obtaining tungstenite nanoparticles directly into a monomer (tetraethyleneglycol diacrylate), to be eventually polymerized without any further manipulation. The resulting liquid dispersions were characterized by Raman, transmission electron and scanning electron microscopies. Eventually, they were directly used for preparing nanocomposites containing a relatively large amount of exfoliated tungstenite. Differential scanning calorimetry and thermogravimetric analyses were performed in order to assess the effect of the presence of the exfoliated nanofiller on the thermal features of the polymer matrix: a clear improvement of the thermal and thermo-oxidative stability was observed. At variance, the effect of the exfoliated tungstenite on the glass transition temperature of the polymer matrix was negligible. Furthermore, the mechanical behavior of the obtained nanocomposites was evaluated by means of flexural and shore A hardness tests: the exfoliated nanofiller turned out to exert a strong reinforcing effect on the polymer matrix even at very low concentration.
Available from: Daqiang Gao
- "Murugan et al. revealed by first-principles calculations that stoichiometric Mo
(n = 1, 2, 5, and 6) and W6S12 clusters as well as several of the nonstoichiometric clusters are magnetic, where the magnetic moments arise due to the partially filled d states . Besides, calculation results indicate that adsorption of nonmetal elements on the surface of WS2 nanosheets can induce a local magnetic moment . In an experimental study, Matte et al. fabricated WS2 nanosheets by hydrothermal method and revealed their ferromagnetism, which was considered to be related to the edges and defects . "
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ABSTRACT: Two-dimensional-layered transition metal dichalcogenides nanosheets have attracted tremendous attention for their promising applications in spintronics because the atomic-thick nanosheets can not only enhance the intrinsic properties of their bulk counterparts, but also give birth to new promising properties. In this paper, ultrathin tungsten disulfide (WS2) nanosheets were gotten by liquid exfoliation route from its bulk form using dimethylformamide (DMF). Compared to the antiferromagnetism bulk WS2, ultrathin WS2 nanosheets show intrinsic room-temperature ferromagnetism (FM) with the maximized saturation magnetization of 0.004 emu/g at 10 K, where the appearance of FM in the nanosheets is partly due to the presence of zigzag edges in the magnetic ground state at the grain boundaries.
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ABSTRACT: The geometric and electronic structures of graphene adsorption on MoS(2) monolayer have been studied by using density functional theory. It is found that graphene is bound to MoS(2) with an interlayer spacing of 3.32 Å and with a binding energy of -23 meV per C atom irrespective of adsorption arrangement, indicating a weak interaction between graphene and MoS(2). A detailed analysis of the electronic structure indicates that the nearly linear band dispersion relation of graphene can be preserved in MoS(2)/graphene hybrid accompanied by a small band-gap (2 meV) opening due to the variation of on-site energy induced by MoS(2). These findings are useful complement to experimental studies of this new synthesize system and suggest a new route to facilitate the design of devices where both finite band-gap and high carrier mobility are needed.
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