Wang Mu;Wu Di;Tsukamoto Katsuo

Aip Conference Proceedings

2010

Based on first-principles calculations of the rutile TiO2 (110) surface with different types of oxygen vacancies, a phase diagram is constructed for the energetically favorable oxygen vacancy as a function of the externally applied in-plane strain. When the strain is relatively small, the bridging oxygen vacancy (BOV) is the energetically favorable one. The pathways and the energy barriers of surface diffusion of the BOV under different external strain are studied. For the cross row diffusion of the BOV along [1 1̄ 0], a concerted diffusion mechanism mediated by the in-plane oxygen vacancy is found to be energetically more favorable than the hopping diffusion. The energy barrier of the concerted diffusion along [1 1̄ 0] and that of the hopping diffusion along [001] are found to decrease with increasing strain. The former decreases more dramatically than the latter when the strain is applied along [1 1̄ 0], which suggests a possible way of facilitating the diffusion anisotropy. © 2010 The American Physical Society.

Wang Zhao-Wu;Shu Da-Jun;Wang Mu;Ming Nai-Ben

Physical Review B Condensed Matter and Materials Physics

2010

The SrBi2Ta2O9 (SBT) thin films were prepared by metalorganic decomposition on Pt/TiO2/SiO2/Si substrates with rapid thermal annealing (RTA). The films were annealed at different temperature (T) for different time (t) to investigate the crystal growth of the films. The grain size distribution basically conforms to Gaussian distribution and the rate of nucleation is high with RTA. There are two steps in grain growth. First, grain size is proportion to t1/2 before 10s, then proportion to t1/2. The growth activity energy is about 29kJ/mol under 700°C and 81kJ/mol above 700°C. From the results mentioned above we can draw a conclusion that it is easier to grow larger SBT grains by increasing annealing temperature than by lengthening annealing time in RTA. © 2001 Taylor & Francis.

Ling Huiqin;Li Aidong;Wu Di;Wang Mu;Yin Xiaobo;Liu Zhiguo;Ming Naiben

Ferroelectrics

2001

Shu Da-Jun;Ge Shu-Ting;Wang Mu;Ming Nai-Ben

Physical Review Letters

2011

Nanoscale patterned electrodeposition of metals on flat substrates has become a topic of great interest both scientifically and technologically in recent years. Here, we demonstrate the self-organized growth of extended arrays of parallel nanoscale copper wires on flat glass chips from an ultra-thin aqueous electrolyte layer. Regular, periodic patterns of copper nanowires with diameters in the range of 40 nm-400 nm were grown, forming parallel arrays of alternating lines of copper and cuprous oxide at periodicities down to approx. 80 nm, depending on the deposition parameters such as voltage and pH. The resulting multiline films are investigated with respect to their structure and electrical properties using Electrical Force Microscopy, Scanning Electron Microscopy and Scanning Auger Electron Spectroscopy. The results of the experiments show a strongly anisotropic behavior of the electrical properties of multiline nanostructures corresponding to their strongly anisotropic geometry. © 2010 American Scientific Publishers.

Zhong Sheng;Dupeyrat Patrik;Gr\u00f6ger Roland;Koch Thomas;Schimmel Thomas;Wang Mu

Journal of Nanoscience and Nanotechnology

2010

The influences of external strain on diffusion properties of the bulk and subsurface oxygen vacancy (OV) in rutile TiO 2 are systematically studied using first-principle calculations. For OVs in bulk, we find that tensile (compressive) strain applied in the [001] direction or isotropically applied in the equivalent [110] and [11̄0] directions reduces (increases) the energy barriers of diffusion. Anisotropic strain applied in [110] and [11̄0] increases the energy barriers of diffusion in the two directions. Meanwhile it results in anisotropic diffusion behaviors. Between [110] and [11̄0], the bulk OV prefers to diffuse along the one in which more compressive or less tensile strain is applied. From subsurface to surface, the most energetically favorable OV pathway is along the [110] rows terminated with the surface bridging oxygen atoms. The diffusion barrier of the OV in the first trilayer is much lower than that of a bulk OV. External in-plane tensile strain can further reduce the energy barrier of the subsurface OV diffusion, and thus help to improve the diffusion of OVs from bulk to surface. © 2011 Elsevier B.V. All rights reserved.

Wang Zhao-Wu;Shu Da-Jun;Wang Mu;Ming Nai-Ben

Surface Science

2012

Surfaces with high reactivity usually have a low area percentage, which greatly limits the efficiency of surface reactivity. In this Letter we demonstrate a generic way of increasing the percentage of the highly reactive surface by using external strain. Bulk and surface elastic properties of TiO 2 are studied via density functional theory calculations. The equilibrium shape of anatase TiO 2 under applied strain is discussed based on the elastic properties. We find that when 5% compressive strain is applied biaxially along [100] and [010]; directions, the area percentage of the anatase (001) surface can be increased by ∼5 times in comparison with the case when no strain is applied. Since the moderate strain does not introduce extrinsic defects into the material, we propose that it is an ideal way to increase the reactivity of titanium dioxide crystallites by applying biaxial compressive external strain along the a axis. © 2012 American Physical Society.

Jia Lan;Shu Da-Jun;Wang Mu

Physical Review Letters

2012

Generally, it is well known that the lithium-ion diffusion in olivine LixFePO4 is correlated with the phase transition dominated by a domino-cascade model instead of a core-shell model. Based on the experiment result, we firstly found that the linear Warburg region of electrochemical impedance spectra should tilt with a small angle of 30° for the domino-cascade model, while the core-shell model should correspond to a traditional angle of about 45°. Considering that the measured Warburg impedance varies along the charge and discharge processes, we firstly proposed a hybrid phase-transition model as a combination of the domino-cascade model and the core-shell model to describe the olivine LixFePO4. And this hybrid model was possibly attributed to both the strong anisotropy in the bulk of olivine LixFePO4 and the different properties between the lithiated and delithiated phases. Potentially, this micro-mechanism could be extended to some other two-phase electrode active materials in lithium ion batteries. © 2013 Elsevier B.V. All rights reserved.

Li De;Zhang Tao;Liu Xizheng;Zhou Haoshen;He Ping;Peng Ruwen;Wang Mu;Han Min

Journal of Power Sources

2013

In this paper, we theoretically demonstrate that electromagnetic transparency can be induced by optical magnetism in a metamaterial, which is composed of metamolecules. Each metamolecule consists of a metallic split-ring resonator, as one bright meta-atom (which is optically magnetic), and also a cut-wire pair, as one dark meta-atom (which is optically nonmagnetic). It is found that magnetic resonances occur at optical frequencies due to the local magnetic interaction between "bright" meta-atoms and "dark" meta-atoms; thereafter, a transparency window emerges upon the original absorption background. The phenomenon is similar to the electromagnetically induced transparency (EIT) in atomic three-level systems, and a microscopic picture is given to compare it with the EIT. Furthermore, low loss and slow light in this metamaterial have also been verified. The investigations may achieve potential applications on integrated optical circuits. © 2013 American Physical Society.

Qin Ling;Zhang Kun;Peng Ru-Wen;Xiong Xiang;Zhang Wei;Wang Mu;Huang Xian-Rong

Physical Review B Condensed Matter and Materials Physics

2013

In this work, we investigate the coupling of surface plasmons and excited optical modes in metal/dielectric grating stacks theoretically and experimentally. We have observed three kinds of modes in these structures: the cavity mode, the propagated surface plasmon (PSP) mode and the localized surface plasmon (LSP) mode, which can enhance the optical transmission. Firstly, it is shown that the cavity mode is excited in the grating stacks. And the cavity mode has redshift if we enhance the thickness of metal layers, while it has blueshift when we increase the thickness of dielectric layers. The redshift of the cavity mode also occurs when the number of repeating layers is increased. Secondly, the PSP mode is also excited, which can be described by the effective permittivity method. It is found that the PSP modes are coupled with each other, which leads to a modified dispersion relation of surface plasmon polaritons (SPP). The theoretical analysis is in good agreement with the observed transmission enhancement in the grating stacks. And the coupling of PSPs also leads to a blueshift when the number of metal layers is increased. Thirdly, the LSP mode, generated in single metal strip, can also enhance the optical transmission of the grating stacks. Yet the transmission intensity induced by LSP decreases rapidly with increasing the number of metal layers. The investigations here may have potential applications in designing plasmonic metamaterials and subwavelength optical devices. Copyright © 2013 American Scientific Publishers All rights reserved.

Fan Ren-Hao;Qi Dong-Xiang;Hu Qing;Qin Ling;Peng Ru-Wen;Wang Mu

Journal of Nanoscience and Nanotechnology

2013