Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers
ABSTRACT 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.
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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.Composites Science and Technology 05/2014; 96. DOI:10.1016/j.compscitech.2014.03.015 · 3.63 Impact Factor
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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.Nanoscale 08/2011; 3(9):3883-7. DOI:10.1039/c1nr10577a · 6.74 Impact Factor
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ABSTRACT: Following the two-dimensional periodic single-layer sheet successful synthesized experimentally very recently [Adv. Mater., 2011, 23, 4497], we present systematically the electronic and magnetic properties of this novel polymer (referred to as C(4)H) without and with strain-modifying, vacancy-doping, and nonmetal element (B, N, and P) doping by means of first-principles calculations. It was found that: (a) the C(4)H sheet is a nonmagnetic semiconductor with a wide indirect band gap. (b) The atomic structure, binding energies and electronic properties of the C(4)H sheet could be significantly modified by applying strain. (c) Vacancy defects can lead to intrinsic magnetism in C(4)H and, surprisingly, the induced spin polarization has large spatial extension; especially, room-temperature ferromagnetism in H vacancies-doped case is quite feasible. (d) Substitution of B, P and N at the unhydrogenated C site could form a local magnetic moment, whereas no spin-polarization could be induced for that with N at the hydrogenated C site. The present study provides theoretical insight leading to a better understanding of novel 2D structures, and further experimental studies are expected to confirm the attractive predictions.Physical Chemistry Chemical Physics 02/2012; 14(10):3651-8. DOI:10.1039/c2cp23494g · 4.20 Impact Factor