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Energy band-gap Calculation of d-Ta_2O_5 Using sX-LDA and B3LYP Methods

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Journal of Wuhan University of Technology(Materials Science) 2015年第1期30卷 43-46页

作者：张光磊 GUO Xiaoyu LI Xuewen QIN Guoqiang FU Hua Hebei Provincial Key Laboratory of Traffic Engineering Materials Shijiazhuang Tiedao University School of Materials Science and Engineering Shijiazhuang Tiedao University Zhengzhou Research Institute for Abrasives & Grinding Co. Ltd.

The energy band-gap and related factors of tantalum pentoxide with hexagonal phase were investigated using hybrid functional B3LYP and sX-LDA methods. The results showed that both sX-LDA and B3LYP techniques reveal the indirect semiconductor nature of δ-Ta2O5, whereas the obtained value of energy band-gap is much higher than previous theoretical reports but closer to the experimental data. The optical band- gap of δ-Ta2O5 is expected to originate from the O 2p→Ta 5d transition which may benefit from the d-s-p hybridization.

关键词： Ta2O5 B3LYP hexagonal phase sX-LDA band-gap

Flexural wave band-gaps in phononic metamaterial beam with hybrid shunting circuits

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Chinese Physics B 2015年第3期24卷 269-274页

作者：张浩温激鸿陈圣兵王刚温熙森 Vibration and Acoustics Research Group Laboratory of Science and Technology on Integrated Logistics SupportCollege of Mechatronics and AutomationNational University of Defense Technology

Periodic arrays of hybrid-shunted piezoelectric patches are used to control the band-gaps of phononic metamaterial beams. Passive resistive-inductive （RL） shunting circuits can produce a narrow resonant band-gap （RG）, and active negative capacitive （NC） shunting circuits can broaden the Bragg band-gaps （BGs）. In this article, active NC shunting circuits and passive resonant RL shunting circuits are connected to the same piezoelectric patches in parallel, which are usually called hybrid shunting circuits, to control the location and the extent of the band-gaps. A super-wide coupled band-gap is generated when the coupling between RG and the BG occurs. The attenuation constant of the infinite periodic structure is predicted by the transfer matrix method, which is compared with the vibration transmittance of a finite periodic structure calculated by the finite element method. Numerical results show that the hybrid-shunting circuits can make the band-gaps wider by appropriately selecting the inductances, negative capacitances, and resistances.

关键词： phononic metamaterial band-gap hybrid shunting circuits flexural wave

band Structure of Three-dimensional Phononic Crystals

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Chinese Journal of Chemical Physics 2006年第2期19卷 155-158页

作者：颜琳赵鹤平王小云黄国盛彭秀艳吉首大学物理科学与信息工程学院

By using the plane-wave-expansion method, the band structure of three-dimension phononic crystals was calculated, in which the cuboid scatterers were arranged in a host with a face-centered-cubic （FCC） *** influences of a few factors such as the component materials, the filling fraction of scatterers and the ratio （RHL） of the scatterer＇s height to its length on the band-gaps of phononic crystals were *** is found that in the three-dimension solid phononic crystals with FCC structure, the optimum case to obtain band-gaps is to embed high-velocity and high-density scatterers in a low-velocity and low-density host. The maximum value of band-gap can be obtained when the filling fraction is in the middle value. It is also found that the symmetry of the scatterers strongly influences the band-gaps. For RHL＞1, the width of the band-gap decreases as RHL increases. On the contrary, the width of the band-gap increases with the increase of RHL when RHL is smaller than 1.

关键词： Phononic crystals band-gap Face-centered-cubic (FCC) Plane wave expansion method

First-principles investigation of BAs and B_xGa_(1-x)As alloys

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Chinese Physics B 2008年第8期17卷 3062-3066页

作者：熊德平周守利王琦任晓敏 School of Physics and Optoelectronic Engineering Guangdong University of Technology College of Information Engineering Zhejiang University of Technology Key Laboratory of Optical Communication and Lightwave Technologies Ministry of Education Beijing University of Posts and Telecommunications

First-principles investigation of BAs and BxGa1-xAs alloys Using first-principles calculations in the generalized gradient approximation, the electronic properties of BAs and BxGa1-xAs alloys are studied. At the Brillouin-zone centre, the lowest conduction band is the three-degenerate p-like Г15c state rather than s-like Г1c state, and the conduction band minimum （CBM） is along the A line between the Г and X points-at approximately 11/14（1,0,0）2π/a. With boron content at 0%-18.75%, BxGa1-xAs alloys have a small （2.6 eV） and relatively composition-independent band-gap bowing parameter, the band-gap increases monotonically by -18meV/B% with increasing boron content. In addition, the formation enthalpies of mixing for BxGa1-xAs alloys with boron content at 6.25% and 12.5% are calculated, and the large formation enthalpies may explain the difficulty in alloying boron to GaAs.

关键词： bowing parameter formation enthalpy band-gap boride alloys

Ultraviolet and Deep-Ultraviolet Emissions from c-MgxZn1-xO/MgO Ultrathin Multilayer Heterostructures

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Chinese Physics Letters 2005年第10期22卷 2688-2691页

作者：余萍邱东江吴惠桢 Department of Physics Zhejiang University Hangzhou 310027 State Key Laboratory of Silicon Materials Zhejiang University Hangzhou 310027

Cubic phase MgxZn1-x O/MgO multilayer heterostructures （c-Mgx Zn1-xO/MgO MHs） are grown on Si（100） and quartz substrates by reactive electron beam evaporation at low temperature （250℃）. Cross-sectional morphology observations by field-emission scanning electron microscopy show the legible interfaces of c-MgxZn1-x O/MgO MHs. X-ray diffraction demonstrates that c-MgxZn1-xO/MgO MHs are of highly （100）-oriented. Optical trans- mission investigations of c-Mgx Zn1-x O/MgO MHs on quartz substrates reveal the coexistence of the two phases, c-MgxZn1-xO and MgO. Photoluminescence examination indicates the emergence of deep-ultraviolet emission centred at about 290nm along with the blue shift of the ultraviolet emission from 405nm to 39Gnm when the nominal thickness of c-MgxZn1-xO well layers of MHs is diminished to 3nm, which is probably originated from quantum confinement effect.

关键词： ZNO/ZNMGO MULTIQUANTUM WELLS THIN-FILMS ROOM-TEMPERATURE QUANTUM-WELLS band-gap MGXZN1-XO GROWTH SUBSTRATE SI(111) ALLOY

Growth and Characterization of InN Thin Films on Sapphire by MOCVD

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Chinese Physics Letters 2007年第4期24卷 1004-1006页

作者：谢自力张荣修向前刘斌李亮韩平顾书林施毅郑有炓 Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Department of Physics Nanjing University Nanjing 210093

Indium nitride thin films are grown on sapphire substrates by metal-organic chemical vapour deposition （MOCVD） By employing three-step layer buffers, the mirror-like layers on two-inch sapphire wafers have been obtained. The structural, optical and electrical characteristics of InN are investigated by x-ray diffraction, scanning electron microscopy, atomic force microscopy, photoluminescence and infrared optical absorption. The photoluminescence and the absorption studies of the materials reveal a marked energy bandgap structure around 0.70eV at room temperature. The room-temperature Hall mobility and carrier concentration of the film are typically 939 cm^2 /Vs, and 3.9 × 1018cm^-3, respectively.

关键词： MOLECULAR-BEAM EPITAXY LOW-TEMPERATURE band-gap RF-MBE ALLOYS

Direct Observation of NN Pairs Transfer in gap1-xNx （x=0.12%）

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Chinese Physics Letters 2005年第11期22卷 2957-2959页

作者：吕毅军高玉琳郑健生张勇 MASCARENHAS A. 辛火平杜武青 Department of Physics Xiamen University Xiamen 361005 National Renewa-ble Energy Laboratory 1617 Cole Blvd. Golden Colorado 80401USA Department of Electrical and Computer Engineering University of California California 92093-0407 USA

Time-resolved photoluminescence （TRPL） was applied to investigate the transient process in gap1-xNx （x = 0.12%） alloy. The filling, transferring and decay processes among nitrogen pairs are directly observed. The NN4 pair, either not present or only a small obscure peak under a proper excitation condition in the steady-state photoluminescence spectrum, is well resolved by TRPL.

关键词： NITROGEN-BOUND EXCITONS band-gap ALLOYS PHOTOLUMINESCENCE DEPENDENCE TRANSITION EVOLUTION GAASN DECAY TIME

Influence of parameters on light propagation dynamics in optically induced planar waveguide arrays

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Science China(Physics,Mechanics & Astronomy) 2009年第5期52卷 747-754页

作者： LIU Sheng ZHANG Peng XIAO FaJun YANG DeXing ZHAO JianLin Institute of Optical Information Science and Technology and Shaanxi Key Laboratory of Optical Information Technology School of ScienceNorthwestern Polytechnical UniversityXi’an 710072China

The diffraction and refraction of light beam in optical periodic structures can be determined by the photonic band-gap structures of spatial *** this paper,by employing the equation governing the nonlinear light propagations in photorefractive crystals,we study the photonic band-gap structures, Bloch modes,and light transmission properties of optically induced planar waveguide *** relationship between the photonic band-gap structures and the light diffraction characteristics is discussed in *** the influence of the parameters of planar waveguide arrays on the band-gaps structures,Bloch modes,and linear light transmissions is *** is revealed that the linear light transmission properties of waveguide arrays are tightly related to the diffraction relationships determined by band-gap *** the Bloch modes corresponding to different transmission bands can be excited by different excitation *** the increases of the intensity and the period of the array writing beam will lead to the broadening of the forbidden gaps and the concentration of the energy of the Bloch modes to the high-index ***,the broadening of the forbidden gaps will lead to separation and transition between the Bloch modes of neighboring bands around the Bragg ***,with the increase of the intensity of the array writing beams,the influences from light intensity will tend to be steady due to the saturation of the photorefractive effect.

关键词： optically induced planar waveguide array photonic band-gap Bloch modes photorefractive LiNbO3 crystal

The band structures of BSb and B_xGa_(1-x)Sb alloys

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Science China(Physics,Mechanics & Astronomy) 2009年第6期52卷 843-847页

作者： XIONG DePing1, ZHOU ShouLi2, WANG Qi3, LUO Li1, HUANG YongQing3 & REN XiaoMin3 1 School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China 2 College of Information Engineering, Zhejiang University of Technology, Hangzhou 310032, China 3 Key Laboratory of Optical Communication and Lightwave Technologies Ministry of Education, Beijing University of Posts and Telecommunications, Beijing 100876, China School of Physics and Optoelectronic Engineering Guangdong University of Technology Guangzhou China College of Information Engineering Zhejiang University of Technology Hangzhou China Key Laboratory of Optical Communication and Lightwave Technologies Ministry of Education Beijing University of Posts and Telecommunications Beijing China

The band structures of BSb and BxGa1-xSb alloys are studied using first-principles calculations in the generalized gradient approximation. By SQS-8 supercells to model a random alloy, the direct transition energy-gap (Γ15v- Γ1c) bowing of 3.0 eV is obtained for BxGa1-xSb alloys in x = 0-50%, in x = 0-11% the energy-gap is the band-gap and increases by 7 meV/%B with boron composition increasing; by SQS-16 supercells the bowing parameter is about 1.9 eV in x = 0-12.5%. The formation enthalpies of mixing, ΔH, are calculated for BxGa1-xAs and BxGa1-xSb alloys. A comparison of enthalpies indicates that BxGa1-xSb films with boron composition of 7% may be possible.

关键词： band-gap bowing parameter boride alloys