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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

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

Simultaneous achievement of large electrocaloric effect and ultrawide operating temperature range in BaTiO_(3)-based lead-free ceramic

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Journal of Advanced Ceramics 2024年第8期13卷 1234-1241页

作者： Zhaojie Wang Yingzhi Meng Silin Tang Xiang Niu Hongfang Zhang Dingyuan Wang Yisong Bai Bialin Peng Xue Chen Qingqing Ke Sheng-Guo Lu Laijun Liu Guangxi Key Lab of Optical and Electronic Functional Materials and Devices Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of ResourcesCollege of Materials Science and EngineeringGuilin University of TechnologyGuilin 541004China School of Microelectronics Science and Technology Sun Yat-sen UniversityZhuhai 519082China Guangdong Provincial Research Center on Smart Materials and Energy Conversion Devices School of Materials and EnergyGuangdong University of TechnologyGuangzhou 510006China School of Physical Science and Technology&Key Laboratory of Advanced Electrode Materials for Novel Solar Cells for Petroleum and Chemical Industry of China Suzhou University of Science and TechnologySuzhou 215009China Qingdao Haier Smart Technology R&D Co. Ltd.Qingdao 266100China School of Advanced Materials and Nanotechnology Xidian UniversityXi'an 710071China Guangxi Key Laboratory of Manufacturing System&Advanced Manufacturing Technology Guilin University of Electronic TechnologyGuilin 541004China

The electrocaloric effect(ECE),known for its environmentally friendly characteristics,holds significant promise for advancing next-generation solid-state refrigeration *** a large ECE along with a wide working temperature range near room temperature remains a key developmental *** this study,we successfully obtained a substantial ECE of 1.78 K and an extensive working temperature range of 103 K(AT>1.52 K)near room temperature in CaZrO_(3)-modified BaTiO_(3) lead-free ferroelectric ***,this achievement was verified using direct *** piezoresponse force microscopy(PFM)results suggest that the broad temperature range is attributed to the formation of ferroelectric microdomains and polar nanoregions(PNRs).Furthermore,X-ray photoelectron spectroscopy(XPS)and ultraviolet-visible(UV-Vis)spectroscopy reveal a decrease in the oxygen vacancy concentration and an increase in the bandgap for higher CaZrO_(3) doping *** changes synergistically enhance the maximum applied electric field,helping to achieve a high-performance EcE near room *** research presents a straightforward and effective approach for achieving high-performance ECEs in BaTiOg lead-free ceramics,offering promising prospects for application in next-generation solid-state refrigeration technologies.

关键词： BaTiO_(3) electrocaloric effect oxygen vacancy band-gap

Polaronic Tunnelling in Organic Triblock Copolymers

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Chinese Physics Letters 2005年第1期22卷 178-181页

作者：刘德胜张大成解士杰梅良模 SchoolofPhysicsandMicroelectronics ShandongUniversityJinan250100//DepartmentofPhysicsJiningNormalUniversityJining272025//NationalKeyLaboratoryofCrystalMaterialsShandongUniversityJinan250100 SchoolofPhysicsandMicroelectronics ShandongUniversityJinan250100//NationalKeyLaboratoryofCrystalMaterialsShandongUniversityJinan250100

Polaron tunnelling is studied in xPA/nPPP/xPA (PA for polyacetylene and PPPpoly (p-phenylene)) triblock copolymer, which has a well-barrier-well structure. An extendedtight-binding Hamiltonian including external electric held is adopted. Without electric field, theinjected electrons would not extend over the whole copolymer chain but instead be confined in thesegments of PA. This is different from the behaviour of the traditional semiconductors. It is foundthat the polaron can transfer to the potential barrier-PPP segment when the applied electric fieldreaches a certain value. The critical polaron tunnelling electric fields depend upon the lengths ofPPP segments.

关键词： ELECTRONIC-STRUCTURE CONJUGATED POLYMERS band-gap ELECTROLUMINESCENCE POLYACETYLENE OLIGOMERS STATES

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

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

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

Nonlinear Response of One-Dimensional Magneto-Optical Photonic Crystals

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Chinese Physics Letters 2005年第7期22卷 1680-1683页

作者：王为忠 DDepartmentofPhysics WuhanUniversityWuhan430072

We numerically investigate the magneto-optical Cotton-Mouton effect in analternating multilayer structure with a nonlinear dielectric constant. The multistability andpolarization of the transmission of electromagnetic field near the edges of the stop gap are studiedin detail. The resonant transmission is accompanied by solitons of intensity of the field. Thisinvestigation provides a way to select the transmission property with different polarizations sinceboth the amplitude and the phase of the output field can be adjusted by the input power and by themagneto-optical coefficient depending on the external magnetic field.

关键词： OPTICAL-RESPONSE MULTILAYER STRUCTURES band-gap SUPERLATTICES FILM