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Different localized states of travelling-wave convection in a rectangular container

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Chinese Physics B 2006年第12期15卷 2984-2988页

作者：李国栋黄永念 Institute of Water Resources and Hydro-electric Engineering Xi'an University of Technology Xi'an 710048 China State Key Laboratory for Studies of Turbulence and Complex Systems Peking University Beijing 100871 China

We have performed numerical simulations of localized travelling-wave convection in a binary fluid mixture heated from below in a long rectangular container. Calculations are carried out in a vertical cross section of the rolls perpendic- ular to their axes. For a negative enough separation ratio, two types of quite different confined states were documented by applying different control processes. One branch of localized travelling waves survives only in a very narrow band within subcritical regime, while another branch straddles the onset of convection existing both in subcritical and super- critical regions. We elucidated that concentration field and its current are key to understand how confined convection is sustained when conductive state is absolutely unstable, The weak structures in the conducting region are demonstrated too.

关键词： binary fluid mixture travelling-wave convection localized states

Activation of silicon quantum dots for emission

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Chinese Physics B 2012年第9期21卷 295-300页

作者：黄伟其苗信建黄忠梅刘世荣秦朝建 Key Laboratory of Photoelectron Technology and Application Institute of Nanophotonic PhysicsGuizhou University State Key Laboratory of Ore Deposit Geochemistry Institute of GeochemistryChinese academy of Sciences

The emission of silicon quantum dots is weak when their surface is passivated well. Oxygen or nitrogen on the surface of silicon quantum dots can break the passivation to form localized electronic states in the band gap to generate active centers where stronger emission occurs. From this point of view, we can build up radiative matter for emission. Emissions of various wavelengths can be obtained by controlling the surface bonds of silicon quantum dots. Our experimental results demonstrate that annealing is important in the treatment of the activation, and stimulated emissions at about 600 and 700 nm take place on active silicon quantum dots.

关键词： activation for emission silicon quantum dots localized states

Curved surface effect and emission on silicon nanostructures

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Chinese Physics B 2013年第10期22卷 292-298页

作者：黄伟其尹君周年杰黄忠梅苗信建陈汉琼苏琴刘世荣秦朝建 Institute of Nanophotonic Physics Key Laboratory of Photoelectron Technology and ApplicationGuizhou University

The curved surface （CS） effect on nanosilicon plays a main role in the activation for emission and photonic manipulation. The CS effect breaks the symmetrical shape of nanosilicon on which some bonds can produce localized electron states in the band gap. The investigation in calculation and experiment demonstrates that the different curvatures can form the characteristic electron states for some special bonding on the nanosilicon surface, which are related to a series of peaks in photoluminecience （PL）, such as LN, LNO, Lo1, and Lo2 lines in PL spectra due to Si-N, Si-NO, Si=O, and Si-O-Si bonds on curved surface, respectively. Si-Yb bond on curved surface of Si nanostructures can provide the localized states in the band gap deeply and manipulate the emission wavelength into the window of optical communication by the CS effect, which is marked as the Lyb line of electroluminescence （EL） emission.

关键词： silicon nanostructures curved surface effect characteristic line localized states

Activation of silicon quantum dots and coupling between the active centre and the defect state of the photonic crystal in a nanolaser

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Chinese Physics B 2012年第6期21卷 234-238页

作者：黄伟其陈汉琼苏琴刘世荣秦朝建 Institute of Nanophotonic Physics Key Laboratory of Photoelectron Technology and ApplicationGuizhou University State Key Laboratory of Ore Deposit Geochemistry Institute of GeochemistryChinese Academy of Sciences

A new nanolaser concept using silicon quantum dots （QDs） is proposed. The conduction band opened by the quantum confinement effect gives the pumping levels. localized states in the gap due to some surface bonds on Si QDs can be formed for the activation of emission. An inversion of population can be generated between the localized states and the valence band in a QD fabricated by using a nanosecond pulse laser. Coupling between the active centres formed by localized states and the defect states of the two-dimensional （2D） photonic crystal can be used to select the model in the nanolaser.

关键词： nanolaser Si quantum dots localized states photonic crystal

Effect of Zinc additive on dielectric properties of Cd–Se glassy system

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Progress in Natural Science:Materials International 2015年第3期25卷 222-228页

作者： Mohsin Ganaie M.Zulfequar Department of Physics Jamia Millia Islamia

Cd5Se95–xZnx(x=0, 2, 4, 6) glassy alloy has been prepared by a melt-quenching technique. Thin films were deposited by thermal coating unit on ultraclean glass substrate under a vacuum of 10–6Torr. The absence of any sharp peaks in the X-ray diffraction confirms the amorphous nature of thin films. The frequency and temperature dependence of dielectric constant and dielectric loss in the frequency range of 1 kHz to 1 MHz and in the temperature range of 290–370 K were studied. Dielectric dispersion was observed when Zinc(Zn) was incorporated into the Cd–Se *** increase in dielectric parameter with Zn concentration may be due to increase in defect states. The DC conductivity has been reported to investigate the effect of Zn concentration on DC conduction loss. The results are interpreted in term of dipolar theory for Cd5Se95 and Cd5Se93Zn2samples, while the remaining samples have been explained on the basis of DC conduction loss. It was also observed that the DC conductivity increased with the increase of Zinc concentration, which may be due to the decrease in the band gap near Fermi level.

关键词： Amorphous semiconductor localized states DC conductivity Dielectric constant Dielectric loss

Renormalisation Group of Two-dimensional Decagonal Tilings

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Journal of Materials Science & Technology 1999年第4期15卷 348-350页

作者： Yan, XH Ding, JW Yang, QB Iochum, B Xiangtan Univ Dept Phys Xiangtan 411105 Peoples R China CNRS CPT F-13288 Marseille 9 France

We present a new series of two-dimensional decagonal tilings which are connected with each in five transformation rules. In this case, a real-space renormalization group scheme is developed to study physical propertie... 详细信息

关键词： RENORMALIZATION-GROUP TRANSLATIONAL SYMMETRY localized states PENROSE LATTICE QUASICRYSTAL SPECTRUM MAPS

Klein Paradox and Disorder-Induced Delocalization of Dirac Quasiparticles in One-Dimensional Systems

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Communications in Theoretical Physics 2010年第12期 1129-1133页

作者：袁建辉成泽尹淼曾其军张俊佩 Department of Physics Huazhong University of Science and Technology Wuhan 430074 China

Dirac particle penetration is studied theoretically with Dirac equation in one-dimensional systems. We investigate a one-dimensional system with N barriers where both barrier height and well width are constants randomly distributed in certain range. The one-parameter scaling theory for nonrelatiyistic particles is still valid for massive Dirac particles. In the same disorder sample, we find that the localization length of relativistic particles is always larger than that of nonrelativistic particles and the transmission coefficient related to incident particle in both cases fits the form T～ exp（-αL）. More interesting, massless relativistic particles are entirely delocalized no matter how big the energy of incident particles is.

关键词： Anderson localization disordered structures quantum transport localized states