Desheng Liu

Shandong University, Chi-nan-shih, Shandong Sheng, China

Are you Desheng Liu?

Claim your profile

Publications (41)103.57 Total impact

  • Qiu-Hua Wu · Peng Zhao · Desheng Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: Based on the first-principles density functional theory combined with nonequilibrium Green’s function method, we have investigated the spin-dependent transport properties of a pyrene-ZGNR system. The results show that this system can exhibit high-performance spin filtering, spin rectifying, giant magnetoresistance and negative differential resistance effects, by tuning the magnetization configuration of ZGNR electrodes. By analyzing the spin-resolved transmission spectrum, the local density of states, the transmission pathways, the band structure and symmetry of ZGNR electrodes, as well as the spatial distribution of molecular orbitals within the bias window, we elucidate the mechanism for these intriguing properties. Our results suggest that the pyrene-ZGNR system is a potential candidate for developing the high-performance multifunctional spintronic devices.
    No preview · Article · Feb 2016 · RSC Advances
  • [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the effects of edge dehydrogenation on magnetism and spin transport of zigzag graphene nanoribbons (ZGNRs) with line defects (558defect and 57defect) by the first-principles calculations. Results show that magnetization can be induced or strengthened obviously in 558defect-ZGNRs unterminated by hydrogen, but not for 57defect-ZGNRs. This is because a spin-polarized σ edge state appears near the Fermi level and strengthens spin-splitting of energy bands at bare edges of the 558defect-ZGNRs. Moreover, compared with pristine ZGNRs, the 558defect-ZGNRs with bare edges can realize a transition from antiferromagnetic coupling to ferromagnetic coupling between both edges. In addition, the spin-filter efficiency can be effectively improved in our proposed devices by edge dehydrogenation. Our results demonstrate that the presence of σ edge state near the Fermi level plays an important role in controlling spin transport of the graphene-based spintronic devices.
    No preview · Article · Dec 2015 · Organic Electronics
  • Hui Wang · Yuan Li · Dongmei Li · Bin Cui · Desheng Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a model study of the dynamic properties of a polaron in an organic ferromagnetic polymer by focusing on the spin correlation between the polymer backbone and the side radicals. The simulations are performed by using a tight-binding description coupled with a nonadiabatic dynamics method. We find that, in the presence of an external electric field, the polarons with both up and down spins can get trapped near the side radicals of the polymer chain unless the electric field is stronger than a critical field. However, the magnitudes of the critical electric field vary quite differently for the spin-up and spin-down polarons as a function of the number of side radicals in the polymer, leading to the exponential change of the range of the electric field within which the spin-filtering takes place. The range of the electric field increases nearly in a linear manner with the strength of the electron-lattice coupling as a result of the increase of the polaron binding energy. The impact of the strength of the spin correlation between the backbone and the side radicals on the polaron spin filtering is also discussed. These findings are expected to be useful for the design of organic-based spin filters.
    No preview · Article · Nov 2015 · Physical Chemistry Chemical Physics
  • [Show abstract] [Hide abstract]
    ABSTRACT: By using nonequilibrium Green's functions (NEGF) and density functional theory (DFT), we investigate the spin-dependent electronic transport properties of two heterojunctions based on zigzag-edged graphene nanoribbons and graphitic carbon nitrides nanoribbons. The only difference is in the scattering region, i.e., one is zigzag-edged graphene nanoribbons (ZGNRs) and the other is graphitic carbon nitrides (g-C3N4) nanoribons. Our results show that the heterojunctions are promising multifunctional devices in molecular spintronics due to the nearly perfect spin-filtering (SFE) and high rectification ratio (RR). Spin negative differential resistance (SNDR) properties at low biases can also be found in the two devices.
    No preview · Article · Aug 2015 · RSC Advances
  • [Show abstract] [Hide abstract]
    ABSTRACT: A series of n-acene-graphene (n=3, 4, 5, 6) devices, in which n-acene molecules are sandwiched between two Zigzag graphene nanoribbon (ZGNR) electrodes, are modeled through the spin polarized density functional theory combined with non-equilibrium Green’s function technique. Our theoretical results show that with n-acene molecules ranging from anthracene to hexacene, the spin-polarized electronic states near the Fermi level can be induced by the spin-polarized ZGNR electrodes, which strengthen gradually to facilitate the electronic transport. A nearly 100% spin filtering ratio and a dual-orientation spin-rectifying effect are observed in a wide region of bias voltage. Importantly, an over 8000% giant magnetoresistance is obtained in the low bias range from -0.1V to +0.1V. Moreover, negative differential resistance behaviors are detected in these devices. The potential mechanisms for these intriguing phenomena are proposed and these findings would be instructive for the design and synthesis of high-performance graphene-based spin-related devices.
    No preview · Article · Mar 2015 · Physical Chemistry Chemical Physics
  • Qiu-Hua Wu · Peng Zhao · Yan Su · Desheng Liu · Gang Chen
    [Show abstract] [Hide abstract]
    ABSTRACT: Based on spin-polarized first-principles density functional theory combined with nonequilibrium Green’s function method, the thermal spin transport properties of a nitroxide radical-based molecule sandwiched between two Au electrodes are investigated. The results show that the opposite spin currents can be induced by applying a temperature difference, rather than bias voltage, between two electrodes. Moreover, a pure spin current and a completely spin-polarized current can be realized by tuning the transverse gate voltage. These results indicate that the nitroxide radical-based molecule is a potential material for spin caloritronic and spintronic applications.
    No preview · Article · Feb 2015 · RSC Advances
  • [Show abstract] [Hide abstract]
    ABSTRACT: Using nonequilibrium Green’s functions in combination with the density functional theory, we investigate the spin-dependent electronic transport properties of two nanostructure devices based on graphitic carbon nitrides bridging two zigzag graphene nanoribbons, i.e., center and edge bridged devices, respectively. It is found that the center bridged device behaves spin negative differential resistance properties in different bias ranges for the up and down spin current respectively. The edge bridged device presents obvious negative differential resistance only for the down spin current. Moreover, high spin-filtering efficiency over 80% is obtained in the edge bridged device in the bias range of 0–1.0 V. The magnetic properties of these devices suggest promising applications in spintronics and molecular electronics.
    No preview · Article · Dec 2014 · Organic Electronics
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have studied the electronic transport behaviors of dithienylethene-based polymer between two metal surfaces using nonequilibrium Green’s functions combined with density functional theory. The present computational results show that the polymer with closed and open configurations really demonstrates switching behavior which confirms the experimental observation. It is also found that the switching behavior depends on the electronic properties of two configurations of polymer instead of the contact modes. The on-off ratios of conductance between the closed and open configurations reach up to two orders of magnitude. Negative differential resistance and rectification phenomena are also observed in such systems.
    No preview · Article · Aug 2014 · RSC Advances
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We model several Au/conjugated molecule/Au junctions in the presence of molecular geometrical torsions. A rectification ratio of around 10 in the twisty diphenyldipyrimidinyl system is obtained, which is in good agreement with experiment. Deeper insight into the rectification mechanism of the conjugated molecular diodes is presented on the basis of simulations in a set of simpler but similar junctions. The rectification effect (the ratio) is significantly improved with increasing the molecular twist, while the conductance is reduced accordingly. Our results suggest that the rectification can be enhanced by the geometrical-torsion-induced reduction in the conjugation length of organic molecules.
    Full-text · Article · Aug 2014 · Journal of Applied Physics
  • [Show abstract] [Hide abstract]
    ABSTRACT: By applying the asymmetrical gate voltage on the 1,4-bis (fullero[c]pyrrolidin-1-yl) benzene BDC20 molecule, we investigate theoretically its electronic transport properties using the density functional theory and nonequilibrium Green's function formalism for a unimolecule device with metal electrodes. Interestingly, the rectifying characteristic with very high rectification ratio, 91.7 and 24.0, can be obtained when the gate voltage is asymmetrically applied on the BDC20 molecular device. The rectification direction can be tuned by the different gate voltage applying regions. The rectification behavior is understood in terms of the evolution of the transmission spectrum and projected density of states spectrum with applied bias combined with molecular projected self-consistent Hamiltonian states analyses. Our finding implies that to realize and greatly promote rectifying performance of the BDC20 molecule the variable gate voltage applying position might be a key issue.
    No preview · Article · Apr 2014 · RSC Advances
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A series of ferrocenylalkanethiol (HSCnFc) single molecular junctions are modeled and their rectification ratios (RRs) are up to 100 (for HSC11Fc), which agrees with the experiments of Whitesides et al. Not only explanation to the origin of the remarkable large RR is given, but also the reason why one order deviation of RR between HSC11Fc and HSC9Fc is discussed and depicted, which was not pointed out by previous researchers. The single asymmetric accessible molecular orbital (MO) model is evaluated, which is different from the Donor (D)–Acceptor (A) models reported before and a clear negative differential resistance (NDR) behavior is found and explained in the HSC11Fc based device.
    Full-text · Article · Feb 2014 · Organic Electronics
  • Source
    Yuqing Xu · Bin Cui · Guomin Ji · Dongmei Li · Desheng Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: Molecular devices with nitro groups display unique electronic transport properties in experiments. By applying the non-equilibrium Green's function combined with density functional theory, we find that the orientation of the nitro group with respect to the backbone of the molecule has a crucial effect on the device performance and can show unusual experimental phenomena. Furthermore, molecular devices with a nitro group are sensitive to gate voltage and suitable for making effective single molecular field-effect transistors. These results provide an important theoretical support to experiments and the design of future molecular devices by using nitro groups.
    Full-text · Article · Nov 2012 · Physical Chemistry Chemical Physics
  • [Show abstract] [Hide abstract]
    ABSTRACT: The electronic transport properties of a gated Au/(C20)2/Au molecular device are studied using nonequilibrium Green's function in combination with density functional theory. The results show that different applied positions of the external transverse gate voltage can effectively tune the current–voltage (I–V) characteristic of molecular devices. Rectifying behaviors of the device can be realized when the gate voltage is applied asymmetrically on the left C20 molecule, and the rectification directions can also be modulated by the positive or negative value of the gate voltage. These results provide an important theoretical support to experiments and the design of a molecular rectifier.
    No preview · Article · Oct 2012 · RSC Advances
  • JiaSai Ma · HaiMing Dong · DongMei Li · DeSheng Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: By applying non-equilibrium Green’s functions (NEGF) in combination with the density functional theory (DFT), we investigate the electronic transport properties of molecular junctions constructed by OPE derivatives with different side groups combined C60 molecules. The results show that the side groups play an important role in the properties of electron transport. Negative differential resistance (NDR) is observed in such devices. Especially for the molecule with electron-donating group (−OCH3), two NDR appear at different bias voltage regions. And the mechanism is proposed for the NDR behavior, owing to the shift of the molecular orbitals caused by the change in molecule charge.
    No preview · Article · Aug 2012 · Science China: Physics, Mechanics and Astronomy
  • Source
    Peng Zhao · DeSheng Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: By applying non-equilibrium Green’s function in combination with density functional theory, we investigated the electronic transport properties of capped-carbon-nanotube-based molecular junctions with multiple N and B dopants. The results show that the electronic transport properties are strongly dependent on the numbers and positions of N and B dopants. Best rectifying behavior is observed in the case with one N and one B dopants, and it is deteriorated strongly with the increasing dopants. The rectifying direction is even reversed with the change of doping positions. Moreover, obvious negative differential resistance behavior at very low bias is observed in some doping cases.
    Preview · Article · Jun 2012 · Chinese Science Bulletin
  • Kun Gao · Shijie Xie · Sun Yin · Desheng Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: By applying a femtosecond electric pump pulse to a polymer, biexcitons are obtained and the relation between its yield and the photoexciting process is also presented. The simulations are performed within the framework of an extended version of one-dimensional Su–Schrieffer–Heeger tight-binding model combined with a nonadiabatic evolution method. In the discussions, effects of both the photoexciting energy and intensity are considered. The main result is that the yield ratio of biexcitons and excitons increases rapidly with the photoexciting intensity, and there exists a critical photoexciting intensity, beyond which the yield efficiency of biexcitons is even higher than that of excitons. The result theoretically verifies that, by increasing the photoexciting intensity, we can obtain biexcitons efficiently, which is consistent with the experimental speculation.
    No preview · Article · May 2012 · Organic Electronics
  • Source
    Peng Zhao · DeSheng Liu · Wei Liang
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate using the Landauer formalism, which combines both the non-equilibrium Green’s function and density functional theory, the effects of separation and orientation between two electrodes of boron-doped capped-carbon-nanotube-based molecular junctions on negative differential resistance. The results show that this negative differential resistance behavior is strongly dependent on the separation and orientation between the two electrodes. A gap width of 0.35 nm and maximal symmetry achieves the best negative differential resistance behavior.
    Preview · Article · Mar 2012 · Chinese Science Bulletin
  • [Show abstract] [Hide abstract]
    ABSTRACT: Using first-principles calculations, we study the electronic transport properties in Au(C20)2Au molecular junctions with different contact interface configurations: point contact and bond contact. We observe that the transmission through the bond contact is considerably higher than that of point contact. Furthermore, the I–V characteristics are rather different. For the bond contact, we get a metallic behavior followed by a varistor-type behavior. While as for the point contact, the current increases very slowly in a nonlinear way and is one order of magnitude smaller than that of bond contact. We attribute these obvious differences to the distinct contact configurations.
    No preview · Article · Jan 2012 · Physics Letters A
  • Source
    Changfeng Fang · Dongmei Li · Bin Cui · Yuqing Xu · Guomin Ji · Desheng Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: By using nonequilibrium Green’s function in combination with density functional theory, we study the electronic transport properties of two typical π-conjugated molecules (dithiol-benzene and C4S2), sandwiched between two metallic electrodes made of different metals. The presence of two different electrodes leads to Fano resonances at certain energy. As a consequence, electronic transport in future molecular electric circuits can be substantially affected when the molecular devices placed between electrodes with different chemical potentials. The Fano line shapes reveal that there is nonresonant channel when two asymmetric electrodes are employed.
    Full-text · Article · Jan 2012 · Applied Physics Letters
  • Yuqing Xu · Changfeng Fang · Guomin Ji · Wei Du · Dongmei Li · Desheng Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: The electronic transport properties of an all-carbon mechanically controlled molecular device based on carbon nanotubes are studied using non-equilibrium Green's function in combination with density functional theory. A segment of (10,0) single-walled carbon nanutube (SWCNT) is placed concentrically outside a (5,0) SWCNT, namely, a (5,0)@(10,0) double-walled carbon nanotube (DWCNT). It is found that the position, orientation and length scaling of the (10,0) SWCNT have crucial effects on the electronic transport properties of the system. When the (10,0) SWCNT is mechanically pushed forward along the axial direction, alternation of on/off switching behavior under low bias and negative differential resistance behavior under high bias are observed. Significant changes in the electronic transport properties arise when rotating the (10,0) SWCNT around the common axis or adding carbon atom layers in the transport direction. Theoretical explanations are proposed for these phenomena.
    No preview · Article · Nov 2011 · Physical Chemistry Chemical Physics