YANG MING
Email Address
phyym@nus.edu.sg
42 results
Publication Search Results
Now showing 1 - 10 of 42
Publication Glass forming abilities of binary Cu100-x Zrx (34, 35.5, and 38.2 at. %) metallic glasses: A LAMMPS study(2009) Sha, Z.D.; Wu, R.Q.; Lu, Y.H.; Shen, L.; Yang, M.; Cai, Y.Q.; Feng, Y.P.; Li, Y.; PHYSICS; CHEMISTRY; MATERIALS SCIENCE AND ENGINEERINGUsing large-scale atomic/molecular massively parallel simulator (LAMMPS), we have studied the liquid behaviors of Cu61.8 Zr38.2, Cu64.5 Zr35.5, and Cu66 Zr34 amorphous alloys including their pair distribution functions, distributions of Voronoi clusters with different coordination numbers, and mean square displacements of Cu and Zr atoms. Compared to Cu61.8 Zr38.2 and Cu66 Zr34, we found high concentrations of distorted icosahedra with indices of 〈 0,2,8,2 〉 and 〈 0,4,4,4 〉, high numbers of Cu-centered Cu8 Zr5 and Cu9 Zr4 clusters, and reduced atomic diffusivity of Cu and Zr atoms in molten Cu64.5 Zr35.5 alloy. These effects would benefit glass formation in Cu64.5 Zr35.5 alloy. Meanwhile, from the viewpoints of local cluster structure, the majority of the glue atoms are Cu atoms in Cu64.5 Zr35.5 amorphous alloy, which leads to denser packing and better glass forming ability. © 2009 American Institute of Physics.Publication Atomic and electronic structures at ZnO and ZrO 2 interface for transparent thin-film transistors(2010-07) Wang, S.J.; Wong, T.I.; Chen, Q.; Yang, M.; Wong, L.M.; Chai, J.W.; Zhang, Z.; Pan, J.S.; Feng, Y.P.; PHYSICSIn this paper, we report the studies of atomic and electronic structures at ZnO and ZrO 2 interface. The epitaxial heterostructures were grown by laser molecular beam epitaxy and the interface atomic structure was determined by using highresolution transmission electron microscopy (TEM). Band alignment for high-k ZrO 2 layer on ZnO was investigated by in situ X-ray photoemission spectroscopy (XPS) characterization and first-principles calculations based on density functional theory (DFT). The valence and conduction band offsets (CBOs) were found to be 0.27±0.05 eV and 2.16±0.05 eV, respectively. The results are in good agreement with values from theoretical calculations. The large CBO and small lattice mismatch between ZnO and ZrO 2 suggest potential for ZrO 2 to be used as a gate dielectric in ZnO-based transparent electronic devices. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Publication Graphene oxide: An ideal support for gold nanocatalysts(2012-10-25) Yang, M.; Zhou, M.; Zhang, A.; Zhang, C.; PHYSICSVia ab initio calculations, we predict that compared with pristine graphene, graphene oxide (GO) is a much better candidate for support of metal (in particular, gold) nanocatalysts in terms of activity and feasibility. Using Au 8 clusters supported on GO as model catalysts, we show that the reaction barrier of the catalyzed CO oxidation can be greatly reduced from around 3.0 to 0.2 eV without the need of defects or strain in the underlying support. The origin of the substantially enhanced activity of Au catalysts is the charge transfer between the GO and supported Au clusters, resulting in activated positively charged Au 8 clusters. Both Langmuir-Hinshelwood and Eley-Rideal mechanisms of the reaction are investigated. We expect our theoretical predictions to stimulate new experiments in the application of GO, one of the most important chemical derivative of graphene, in nanocatalysis. © 2012 American Chemical Society.Publication Orientation control of epitaxial Ge thin films growth on SrTiO 3 (100) by ultrahigh vacuum sputtering(2012-05-31) Deng, W.; Yang, M.; Chai, J.; Wong, T.I.; Du, A.; Ng, C.M.; Feng, Y.; Wang, S.; PHYSICSWe report the orientation control of crystalline Ge (111) and Ge (001) growth on SrTiO 3 (100) substrate by adjusting the temperature of substrate. It is found that the substrate temperature plays an important role for the formation of crystalline Ge with different surface orientations and interfacial chemical configuration during the sputtering process. At 500 °C, Ge (111) with good crystalline quality is formed, while Ge (001) is preferably grown on SrTiO 3 substrate at 650 °C. Our results show the possibility of manipulating the surface orientations during Ge growth on SrTiO 3 by controlling the substrate temperatures. © 2012 Elsevier B.V. All rights reserved.Publication Electrically tunable in-plane anisotropic magnetoresistance in topological insulator BiSbTeSe2 Nanodevices(American Chemical Society, 2015) Lu Y.; Xu W.; Zeng M.; Yao G.; Shen L.; Yang M.; Luo Z.; Pan F.; Wu K.; Das T.; He P.; Jiang J.; Martin J.; Feng Y.P.; Lin H.; Wang X.-S.; PHYSICSPublication Band alignments at SrZrO3/Ge(0 0 1) interface: Thermal annealing effects(2010-05-15) Yang, M.; Deng, W.S.; Chen, Q.; Feng, Y.P.; Wong, L.M.; Chai, J.W.; Pan, J.S.; Wang, S.J.; Ng, C.M.; PHYSICSHigh-κ dielectrics SrZrO3 were prepared on Ge(0 0 1) substrate using pulse laser deposition, and band alignments and thermal annealing effects were studied with high resolution X-ray photoemission spectroscopy. Valence and conduction band offsets at this interface were measured to be 3.26 eV and 1.77 eV, respectively. Interfacial Ge oxide layers were found at the interface. After annealing at 600° C, the interfacial Ge oxide layers were eliminated, and the valence band offset increased to 3.50 eV, but the amorphous SrZrO3 became polycrystalline in the meantime. © 2010 Elsevier B.V. All rights reserved.Publication First principles study of Bismuth alloying effects in GaAs saturable absorber(2012-05-07) Li, D.; Yang, M.; Zhao, S.; Cai, Y.; Feng, Y.; PHYSICSFirst principles hybrid functional calculations have been carried out to study electronic properties of GaAs with Bi alloying effects. It is found that the doping of Bi into GaAs reduces the bandgap due to the intraband level repulsions between Bi induced states and host states, and the Bi-related impurity states originate from the hybridization of Bi-6p and its nearest As-4p orbitals. With the increase of Bi concentration in GaAs, the bandgap decreases monotonously. The calculated optical properties of the undoped and Bi-doped GaAs are similar except the shift toward lower energy of absorption edge and main absorption peaks with Bi doping. These results suggest a promising application of GaBixAs1-x alloy as semiconductor saturable absorber in Q-switched or mode-locked laser. © 2012 Optical Society of America.Publication Ab initio study on intrinsic defect properties of germanium nitride considered for gate dielectric(2007) Yang, M.; Wang, S.J.; Peng, G.W.; Wu, R.Q.; Feng, Y.P.; PHYSICSFirst-principles calculations based on density-functional theory and local-density approximation were carried out to investigate intrinsic defect properties in Β- Ge3 N4. It was found that nitrogen vacancies are the main source of intrinsic defects in Ge3 N4 due to their low formation energy. The N vacancies might become charge trapping centers since they induce energy levels near the Ge conduction band edge and in the middle of the Ge3 N4 band gap. The formation energy of intrinsic defects in Ge3 N4 is sensitive to N chemical potential, and N-rich ambient is favorable to reduce the concentration of N vacancies. © 2007 American Institute of Physics.Publication First principles study of the ternary complex model of EL2 defect in GaAs saturable absorber(2012-03-12) Li, D.; Yang, M.; Cai, Y.; Zhao, S.; Feng, Y.; PHYSICSFirst principles calculations are performed for the perfect GaAs crystal, the double Ga vacancies (VGa)2, and the ternary complex defect (AsGaVAsVGa), using the state-of-the-art computational method with the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional to correct the band gap and account for a proper description of the interaction between defects states and bulk states. Three shallow acceptor defect levels are found due to the creation of (VGa)2 with nearest-neighbor As dangling bonds. However, for GaAs with the ternary complex defects (AsGaVAsVGa), the As antisite AsGa and the VAs's nearest-neighbor Ga dangling bonds provoke several donor defect states. The lowest donor defect state locates at 0.85 eV below the bottom of conduction band, which is very close to the experimental observation of the EL2 defect level. In addition, structual evolution from (VGa)2 defect to the ternary defect complex (AsGaVAsV Ga) is simulated by ab initio molecular dynamic (MD) calculation at different temperatures. The MD results demonstrate that the ternary complex defect (AsGaVAsVGa) can be converted from the double Ga vacancies (VGa)2 at room temperature, and it can exist stably at higher temperature. The present work is helpful to unravel the microstructure and the forming mechanism of the EL2 defect, to find out methods to improve the performance of the GaAs saturable absorber by changing the growth conditions of GaAs crystal. © 2012 Optical Society of America.Publication Possible efficient p-type doping of AlN using Be: An ab initio study(2007) Wu, R.Q.; Shen, L.; Yang, M.; Sha, Z.D.; Cai, Y.Q.; Feng, Y.P.; Huang, Z.G.; Wu, Q.Y.; PHYSICS; CHEMISTRYSpin density functional theory based ab initio study is carried out to investigate the feasibility of fabricating p -type AlN using Be as an efficient dopant. It is found that substitutional BeAl is an acceptor with an activation energy of 0.34 eV. To overcome the low solubility of direct incorporation of Be into AlN and self-compensation from Be interstitials, we propose a hydrogen-assisted growth scheme which improves the solubility and suppresses interstitials. Oxygen is also found to be an effective codopant to activate Be in AlN. Our results suggest the possibility of improving p -type conductivity of AlN by Be doping. © 2007 American Institute of Physics.