Xiangyang Peng

Xiangtan University, Siangtan, Hunan, China

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Publications (22)65.56 Total impact

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    ABSTRACT: Based on first-principles calculations in the framework of van der Waals density functional theory, we find that giant, Rashba-like spin splittings can be induced in both the surface states and quantum well states of thin Bi2Se3 films by application of an external electric field. The charge is redistributed so that the Dirac cones of the upper and lower surfaces become nondegenerate and completely gapless. Interestingly, a momentum-dependent spin texture is developed on the two surfaces of the films. Some of the quantum well states, which reside in the middle of the Bi2Se3 film under zero field, are driven to the surface by the electric field. The Rashba splitting energy has a highly non-linear dependence on the momentum and the electric field due to the large contribution of the high-order Rashba terms, which suggests complex spin dynamics in the thin films of Bi2Se3 under an electric field.
    Journal of Physics Condensed Matter 08/2014; 26(39):395005. · 2.22 Impact Factor
  • physica status solidi (RRL) - Rapid Research Letters 03/2014; · 2.39 Impact Factor
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    ABSTRACT: We have carried out first-principles calculations and theoretical analysis to explore the structural and electronic properties of MoS2/n-h-BN heterostructures consisting of monolayer MoS2 on top of h-BN substrates with one to five layers. We find that the MoS2/n-h-BN heterostructures show indirect bandgap features with both of CBM (in the K point) and VBM (in the Γ point) localized on the monolayer MoS2. Difference charge density and surface bands indicate there is no obvious charge exchange in the heterostructure systems. We show that the changes from a direct bandgap in monolayer free-stranding MoS2 to an indirect bandgap in MoS2/n-h-BN heterostructure is induced by the strain. Moreover, we find that the bandgaps of MoS2/n-h-BN heterostructures decrease with increasing number of h-BN layers, which is proposed to result from the different strain distributions in MoS2 due to the varieties of lattice mismatch rates between MoS2 and h-BN layers. Our results suggest that the MoS2/n-h-BN heterostructure could serve as a prototypical example for band structure engineering of 2D crystals with atomic layer precision.
    01/2014; 47(7).
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    ABSTRACT: Adsorption of hydrogen and hydrocarbon molecules on semiconductor surfaces plays a key role in surface science and technology. Most studies have employed silicon (Si) as a substrate because of its paramount technological importance and scientific interest. However, other semiconductor substrates are gaining an increasing interest as well. Silicon carbide (SiC), which is a material with very special properties allowing developments of novel devices and applications, offers particularly fascinating new degrees of freedom for exceptional adsorption behaviour. For example, a very unusual hydrogen-induced metallization of a SiC(001) surface has been reported and hydrogen molecules show very different adsorption behaviour on different SiC(001) reconstructions although the latter exhibit very similar surface dimers. In marked contrast to the Si(001) surface, the adsorption of hydrocarbon molecules on SiC(001) can yield structurally well-defined adlayers in favourable cases which may have large potential for organic functionalization. We review and discuss theoretical ab initio results on conceivable adsorption scenarios of atomic and molecular hydrogen as well as acetylene, ethylene, butadiene, benzene and cyclohexadiene on various reconstructions of the SiC(001) surface. The main emphasize is on a detailed understanding of these adsorption systems and on identifying the physical origin of the particular adsorption behaviour. The results will be discussed in the light of related adsorption events on the Si(001) surface and in comparison with available experimental data.
    Surface Science Reports 01/2014; 69(s 2–3):55–104. · 15.33 Impact Factor
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    ABSTRACT: Functionalization of MoS2 sheet (monolayer and bilayer) by the adsorption of transition metal Fe adatom to its surface and interlayer has been investigated computationally using first-principles calculations based on the density functional theory. We found that the systems with absorption of Fe adatoms on the surfaces of both monolayer and bilayer MoS2 sheets are still semiconductors, without spin polarization at the Fermi level. However, for the system with absorption of Fe adatom in the interlayer of bilayer MoS2 sheet, its electronic structure exhibits half-metal behavior, with 100% spin polarization at the Femi level, which provides a promising material for spintronic devices.
    Journal of Applied Physics 08/2013; 114(8). · 2.21 Impact Factor
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    ABSTRACT: Based on van der Waals density functional calculations, we have studied few-quintuple-layer (QL) films of Bi2Se3 and Bi2Te3. The separation between the QLs near the surface is found to have a large increase after relaxation, whereas, the separation between the inner QLs is smaller and approaches the bulk value as the thickness grows, showing a two-dimensional to three-dimensional structural crossover. Accordingly, the surface Dirac cone of the Bi2Se3 film is evidently gapped for small thicknesses (two to four QLs), and the gap is reduced and, finally, is closed with the increasing thickness, agreeing well with the experiments. We further studied the substrate effect by investigating the Bi2Se3/graphene system. It is found that the underlying graphene induces a giant thickness-dependent Rashba splitting and Dirac point shift. Because Bi2Te3 films have smaller relative inter-QL expansion and stronger spin-orbit coupling, the topological features start to appear in the film as thin as two QLs in good accord with the experiments.
    Physical review. B, Condensed matter 05/2013; 87(20). · 3.77 Impact Factor
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    ABSTRACT: Two-dimensional MoS2-based materials are considered to be one of the most attractive materials for next-generation nanoelectronics. The electrostatic properties are important in designing and understanding the performance of MoS2-based devices. By using Kelvin probe force microscopy, we show that few-layer MoS2 sheets exhibit uniform surface potential and charge distributions on their surfaces but have relatively lower surface potentials on the edges, folded areas as well as defect grain boundaries.
    AIP Advances. 04/2013; 3(4).
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    ABSTRACT: We studied the nanoindentation of monolayer graphene by molecular dynamics simulations. It is found that the response of graphene to indentation is deflection dependent. In small deflection range, the response obeys point load model, while large-deflection indentation follows the sphere load model. Hence, we proposed to make sectional fittings and use different response models in different deflection ranges. In this way, a consistent Young's modulus is obtained that is almost independent of the size ratio of intender to graphene and the pretensions of graphene. The calculated Young's modulus is about 1.00 TPa, in good agreement with the experiments.
    Applied Physics Letters 02/2013; 102(7). · 3.79 Impact Factor
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    ABSTRACT: Sb2Te3 nanoplates synthesized by vapor phase deposition method have been systemically investigated employing atomic force microscopy, which exhibit regular spiral structures on the surface. The height of spiral steps is determined to be 1 nm corresponding to one quintuple layer, with an inter-step separation ranging from 500 nm to 1 μm. Growth mechanism of spiral structures on the Sb2Te3 nanoplate surface is elucidated, which can be applied to other layered materials with van der Waals epitaxy growth. The electrostatic properties of Sb2Te3 nanoplates with spiral structures are also simultaneously characterized.
    Applied Physics Letters 01/2013; 102(1). · 3.79 Impact Factor
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    ABSTRACT: Based on the first-principle calculations performed by Vienna Ab initio simulation package (VASP), we report the size limitation of half-metallic properties in hybrid zigzag BCN nanoribbons. Both boron–carbon (B–C) and nitrogen–carbon (N–C) interfacial hybrid zigzag BCN nanoribbons are considered. We find that all hybrid systems establish antiferromagnetic ground states. Moreover their electronic properties are mainly determined by the carbon rather than boron nitride segments. Transitions between semiconductor, half-metal and metal can be realized in both systems as the width of the carbon segment increases. However, the half-metallic property can only exist in the systems for which the zigzag carbon chain is less than 6 and 9 for B–C and N–C interfacial systems, respectively. As long as the carbon segment is wider than the above sizes, the systems behave as metals. This effect derives from the electron or hole doping of carbon on the BN segment.
    Physica B Condensed Matter 12/2012; 407(24):4770–4772. · 1.28 Impact Factor
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    ABSTRACT: Based on first-principles calculations within density functional theory, we find that Pb adlayers can induce a giant Rashba spin splitting in the quantum well states of an underlying Bi2Se3 film. As the thickness of the Pb adlayers varies, the distance between the Pb adlayer and the Bi2Se3 film, the charge density at the interface, and the binding between the Pb adlayers exhibit an oscillatory behavior due to the quantum size effects, which in turn modulates the magnitude of the Rashba spin splitting of the quantum well states in the Bi2Se3 film.
    Physical review. B, Condensed matter 10/2012; 86(15). · 3.77 Impact Factor
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    ABSTRACT: Sb2Te3-based nanomaterials are predicted to be one of the topological insulators promising in future spintronics and topological quantum computation. Few-layer Sb2Te3 nanoplates on different substrates forming heterostructures were fabricated via the vapor phase deposition method. The electrostatic properties of Sb2Te3 nanoplates were characterized by Kelvin probe force microscopy. It was found that Sb2Te3 nanoplates exhibit uniform surface potential and charge distribution. The work function was determined to be 5.016 eV for Sb2Te3 nanoplates grown on highly oriented pyrolytic graphite. These results pave a route to explore the exotic topological properties of Sb2Te3-based nanoelectronic devices.
    RSC Advances 10/2012; 2(28):10694-10699. · 3.71 Impact Factor
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    ABSTRACT: A superhard boron nitride phase dubbed as Z-BN is proposed as a possible intermediate phase between h-BN and zinc blende BN (c-BN), and investigated using first-principles calculations within the framework of density functional theory. Although the structure of Z-BN is similar to that of bct-BN containing four-eight BN rings, it is more energetically favorable than bct-BN. Our study reveals that Z-BN, with a considerable structural stability and high density comparable to c-BN, is a transparent insulator with an indirect band gap of about 5.27 eV. Amazingly, its Vickers hardness is 55.88 GPa which is comparable to that of c-BN. This new BN phase may be produced in experiments through cold compressing AB stacking h-BN due to its low transition pressure point of 3.3 GPa.
    Physical Chemistry Chemical Physics 07/2012; 14(31):10967-71. · 4.20 Impact Factor
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    ABSTRACT: Using a generalized genetic algorithm, we propose four new sp(3) carbon allotropes with 5-6-7 (5-6-7-type Z-ACA and Z-CACB) or 4-6-8 (4-6-8-type Z4-A(3)B(1) and A4-A(2)B(2)) carbon rings. Their stability, mechanical and electronic properties are systematically studied using a first-principles method. We find that the four new carbon allotropes show amazing stability in comparison with the carbon phases proposed recently. Both 5-6-7-type Z-ACA and Z-CACB are direct band-gap semiconductors with band gaps of 2.261 eV and 4.196 eV, respectively. However, the 4-6-8-type Z4-A(3)B(1) and A4-A(2)B(2) are indirect band-gap semiconductors with band gaps of 3.105 eV and 3.271 eV, respectively. Their mechanical properties reveal that all the four carbon allotropes proposed in present work are superhard materials, which are comparable to diamond.
    Physical Chemistry Chemical Physics 05/2012; 14(23):8410-4. · 4.20 Impact Factor
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    ABSTRACT: Using first-principles calculations within the framework of density-functional theory, we studied the modulation effect of hydrogen/fluorine chemical decoration on the surface work function of BN sheets. We found that the difference in the work function (ΔWBN) between two surfaces of the chair structure varies with the different decoration. Geometric distortion and chemical effects cause opposite modulation effects, and the chemical effect plays a leading role by inducing charge redistribution in the system.
    AIP Advances. 05/2012; 2(2).
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    ABSTRACT: A superhard boron nitride phase dubbed as Z-BN is proposed as possible intermediate phase between h-BN and zinc blende BN (c-BN), and investigated using first-principles calculations within the framework of the density functional theory. Although the structure of Z-BN is similar to that of bct-BN containing four-eight BN rings, it is more energy favorable than bct-BN. Our study reveals that Z-BN, with a considerable structural stability and high density comparable to c-BN, is a transparent insulator with an indirect band gap about 5.27 eV. Amazingly, its Vickers hardness is 55.88 Gpa which is comparable to that of c-BN. This new BN phase may be produced in experiments through cold compressing AB stacking h-BN due to its low transition pressure point of 3.3 GPa.
    04/2012;
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    ABSTRACT: Two new carbon allotropes (H-carbon and S-carbon) are proposed, as possible candidates for the intermediate superhard phases between graphite and diamond obtained in the process of cold compressing graphite, based on the results of first-principles calculations. Both H-carbon and S-carbon are more stable than previously proposed M-carbon and W-carbon and their bulk modulus are comparable to that of diamond. H-carbon is an indirect-band-gap semiconductor with a gap of 4.459 eV and S-carbon is a direct-band-gap semiconductor with a gap of 4.343 eV. The transition pressure from cold compressing graphite is 10.08 GPa and 5.93 Gpa for H-carbon and S-carbon, respectively, which is in consistent with the recent experimental report.
    Solid State Communications 03/2012; 152(16). · 1.53 Impact Factor
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    Xiangyang Peng, Peter Krüger, Johannes Pollmann
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    ABSTRACT: Adsorption processes of hydrogen molecules on the Si(001)-(2×1) and C(001)-(2×1) surfaces are discussed in light of our previous studies of H2 adsorption on the related SiC(001)-c(4×2) surface. Very amazingly, there are pathways above the latter on which hydrogen molecules can adsorb dissociatively at room temperature. One of these pathways has not been considered before for adsorption of H2 on the Si(001)-(2×1) or C(001)-(2×1) surface. Therefore, we report first-principles investigations of the reaction of molecular hydrogen with the Si(001)-(2×1) and C(001)-(2×1) surfaces on this new adsorption pathway in addition to those that have been studied before. In spite of a number of similarities, the three surfaces show distinct differences as well, giving rise to spectacularly different reactivities with hydrogen molecules. This is due to the fact that the reaction of H2 with semiconductor surfaces depends crucially on intricate combined effects of the arrangement of surface dimers, as well as the orientation of their dangling bond orbitals. In addition, the chemical nature of the surface atoms has a pronounced effect on the spatial extent of dangling bond orbitals which influences the adsorption behaviour markedly as well. In agreement with experiments, our results show that Si(001)-(2×1) and C(001)-(2×1) are inert to H2 adsorption at room temperature for all investigated pathways which exhibit substantial energy barriers. For the two reaction pathways that have been investigated before, our results are in good accord with those of previous density functional and quantum Monte Carlo (QMC) calculations. As a matter of fact, the new reaction channel studied in this work for the first time turns out to have the lowest energy barrier for H2 adsorption on the diamond surface and should thus be the most important channel for sticking of H2 on C(001)-(2×1).
    New Journal of Physics 12/2008; 10(12):125028. · 4.06 Impact Factor
  • Xiangyang Peng, Peter Krüger, Johannes Pollmann
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    ABSTRACT: In a recent experiment, Derycke et al. have made the exciting observation that H2 molecules readily adsorb dissociatively on the c(4×2) but not on the 3×2 surface of SiC(001) at room temperature. To unravel this spectacular reactivity difference, we have investigated a variety of H2 reaction scenarios within density-functional theory using the generalized gradient approximation. It turns out that intradimer adsorption is unlikely at both surfaces, while interdimer adsorption depends crucially on the distinct spatial arrangement and dangling-bond topology of the Si dimers at the surfaces. The results clearly reveal barrierless reaction pathways for dissociative H2 adsorption on the c(4×2) surface as opposed to pathways with significant energy barriers on the 3×2 surface. The latter finding also allows us to explain the inertness of self-organized Si addimer nanolines on the c(4×2) surface to H2 uptake.
    Phys. Rev. B. 02/2007; 75(7).
  • Xiangyang Peng, Peter Krüger, Johannes Pollmann
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    ABSTRACT: We report ab initio investigations of adsorption processes of atomic hydrogen on the SiC(001)-(3×2) surface. In addition to the previously reported hydrogen-induced metallic surface structures, we find semiconducting H adsorption configurations, as well. Most strikingly, the latter turn out to be significantly lower in total energy than the metallic structures. To find out which final adsorption states can actually be reached in experiment, we scrutinize a number of conceivable reaction pathways of additional H atoms from vacuum to different final adsorption sites at the monohydride surface. It turns out that only one of several metallic configurations is most likely, while it appears that semiconducting configurations cannot be realized although they are lower in total energy. Most interestingly, it seems that H does not easily adsorb on the third layer of the monohydride substrate, as suggested previously by experiment and theory because it is captured by a Si atom on the second layer when approaching the third layer from vacuum. On the contrary, H adsorption in angular Si-H-Si bonds on the second layer is easily possible and can explain the experimentally observed hydrogen-induced metallization of the SiC(001)-(3×2) surface.
    Physical review. B, Condensed matter 01/2007; 76(12). · 3.77 Impact Factor