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First-principles study of stability of point defects and their effects on electronic properties of GaAs/AlGaAs superlattice

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Chinese Physics B 2022年第3期31卷 434-443页

作者： Shan Feng Ming Jiang Qi-Hang Qiu Xiang Hua Peng Hai-Yan Xiao Zi-Jiang Liu Xiao-Tao Zu Liang Qiao School of Physics University of Electronic Science and Technology of ChinaChengdu 610054China Department of Physics Lanzhou City UniversityLanzhou 730070China

When the GaAs/AlGaAs superlattice-based devices are used under irradiation environments, point defects may be created and ultimately deteriorate their electronic and transport properties. Thus, understanding the properties of point defects like vacancies and interstitials is essential for the successful application of semiconductor materials. In the present study, first-principles calculations are carried out to explore the stability of point defects in GaAs/Al_(0.5)Ga_(0.5)As superlattice and their effects on electronic properties. The results show that the interstitial defects and Frenkel pair defects are relatively difficult to form, while the antisite defects are favorably created generally. Besides, the existence of point defects generally modifies the electronic structure of GaAs/Al_(0.5)Ga_(0.5)As superlattice significantly, and most of the defective SL structures possess metallic characteristics. Considering the stability of point defects and carrier mobility of defective states,we propose an effective strategy that AlAs, GaAs, and AlGaantisite defects are introduced to improve the hole or electron mobility of GaAs/Al_(0.5)Ga_(0.5)As superlattice. The obtained results will contribute to the understanding of the radiation damage effects of the GaAs/AlGaAs superlattice, and provide a guidance for designing highly stable and durable semiconductor superlattice-based electronics and optoelectronics for extreme environment applications.

关键词： first-principles calculations GaAs/Al_(0.5)Ga_(0.5)As superlattice point defects electronic properties

Influence of monovalent Bi^+doping on real composition,point defects,and photoluminescence in TlCdCl3 and TlCdI3 single crystals

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Science China Materials 2017年第12期60卷 1253-1263页

作者： Daria N.Vtyurina Polina A.Eistrikh-Geller Galina M.Kuz mlcheva Victor B.Rybakov Evgeny V.Khramov Irina A.Kaurova Dmitry Yu.Chernyshov Vladimir N.Korchak Semenov Institute of Chemical Physics Russian Academy of SciencesMOSCOW 119991Russia Institute of Fine Chemical Technologies Moscow Technological UniversityMoscow 119571Russia Lomonosov State University Moscow 119992Russia National Research Center《Kurchatov Instituters》 Moscow 123182Russia Swiss-Norwegian Beamlines at the European Synchrotron Radiation Facility Grenoble 38000France

The structural features and real compositions with point defects of Bi+-doped TlCdCl_3 and TlCdI_3 single crystals, grown by the Bridgman-Stockbarger technique, are first studied using the X-ray diffraction, X-ray synchrotron radiation, and EXAFS/XANES spectroscopy. In the structures of Bi^+-doped TlCdCl_3 and TlCdI_3 crystals, the Cd, Cl, and I sites are found to be defect-free. The vacancies in the Tl sites and interstitial Bi atoms located in the vicinity of the Tl sites are detected in the structures of both samples. In the Bi^+-doped TlCdCl_3, the presence of a small amount of Bi^+ ions in the Tl^+ sites is possible. The correlation between photoluminescence bands and point defects in the refined structures are determined. Photoluminescence spectra and decay kinetics of the Bi+-doped TlCdCl_3 and TlCdI_3 demonstrate that they are attractive materials for potential applications in photonics.

关键词： single crystal growth doping crystal structure point defects photoluminescence

Formation energies and electronic structures of native point defects in potassium dihydrogen phosphate

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Chinese Physics B 2011年第7期20卷 416-420页

作者：王申鹏黄烨 National Center for Materials Service Safety University of Science and Technology Beijing

The formation energies and the equilibrium concentration of vacancies, interstitial H, K, P, O and antisite structural defects with P and K in KH2PO4 （KDP） crystals are investigated by ab initio total-energy calculations. The formation energy of interstitial H is calculated to be about 2.06 eV and we suggest that it may be the dominant defect in KDP crystal. The formation energy of an O vacancy （5.25 eV） is much higher than that of interstitial O （0.60 eV）. Optical absorption centres can be induced by defects of O vacancies, interstitial O and interstitial H. We suggest that these defects may be responsible for the lowering of the damage threshold of the KDP. A K vacancy defect may increase the ionic conductivity and therefore the laser-induced damage threshold decreases.

关键词： KH2PO4 crystal laser-induced damage point defects ab initio

Effect of S Substitution for P point defects in KDP Crystals： First-Principles Study

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Chinese Physics Letters 2010年第7期27卷 80-82页

作者：高慧孙洵刘宝安徐明霞胡国行许心光赵显 State Key Laboratory of Crystal Materials Shandong University Jinan 250100 Department of Physics and Technology Qilu Normal University Jinan 250013 Key Laboratory of Materials for High Power Laser Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800

The electronic structure and geometric distribution of phosphor replaced by sulfur in potassium dihydrogen phosphate （KDP） are investigated by first-principles calculations. The point defect narrows down the energy gap to about 4.9eV, corresponding to a two-photon absorption of 355nm after correction. This can explain the decrease of the laser damage resistance in KDP crystals. Moreover, the defects twist the crystal structure and weaken bonds, especially the O-H bonds, so these bonds may be the first sites to crack under laser irradiation.

关键词： SUBSTITUTION (Technology) ELECTRONIC structure point defects PHOSPHATES SULFUR ENERGY gaps (Physics) ABSORPTION spectra CRYSTALS

A review on the effects of TiO_(2) surface point defects on CO_(2) photoreduction with H_(2)O

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Journal of Materiomics 2017年第1期3卷 17-32页

作者： Huilei Zhao Fuping Pan Ying Li Department of Mechanical Engineering Texas A&M UniversityCollege StationTX 77845USA

Photocatalytic reduction of CO_(2) with water by photocatalysts such as TiO_(2) to produce solar fuels is an attractive approach to alleviate the environmental influences of greenhouse gases and in the meantime produce valuable carbon-neutral *** the materials properties that affect catalytic activity of CO_(2) photoreduction,the point defect on TiO_(2) is one of the most important but not frequently addressed and well understood in the *** this review,we have examined the major influences of TiO_(2) point defects on CO_(2)photoreduction with H_(2)O,by changing the catalysts'gas adsorption capabilities,optical properties,and electronic *** addition,the performances of various defective TiO_(2) toward CO_(2) photoreduction are summarized and compared in terms of productivity,selectivity,and *** hope this review can contribute to understanding the mechanism of CO_(2) photoreduction on defective TiO_(2) and provide insights to the design of highly efficient defect-rich TiO_(2) to boost the CO_(2) utilization.

关键词： CO_(2)photoreduction TiO_(2) Solar fuel Nanostructure point defects Oxygen Vacancy

Calculation studies on point defects in perovskite solar cells

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Journal of Semiconductors 2017年第1期38卷 38-47页

作者： Dan Han Chenmin Dai Shiyou Chen Department of Physics East China Normal UniversityShanghai 200241China Key Laboratory of Polar Materials and Devices(MOE) East China Normal UniversityShanghai 200241China

The close-to-optimal band gap,large absorption coefficient,low manufacturing cost and rapid increase in power conversion efficiency make the organic-inorganic hybrid halide（CH3NH3PbI3）and related perovskite solar cells very promising for *** properties of point defects in the absorber layer semiconductors have important influence on the photovoltaic performance of solar cells,so the investigation on the defect properties in the perovskite semiconductors is necessary for the optimization of their photovoltaic *** this work,we give a brief review to the first-principles calculation studies on the defect properties in a series of perovskite semiconductors,including the organic-inorganic hybrid perovskites and inorganic halide *** identification of these point defects and characterization of their properties are called for.

关键词： point defects perovskite solar cells non-radiative recombination

point defects in epitaxial silicene on Ag(111) surface

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Point defects in epitaxial silicene on Ag(111) surface

Inhibiting the bipolar effect via band gap engineering to improve the thermoelectric performance in n-type Bi_(2-x)Sb_(x)Te_(3)for solid-state refrigeration

中国化学会第30届学术年会-第四十分会：纳米体系理论与模拟

作者： Hongsheng Liu Haifeng Feng Yi Du Jian Chen Kehui Wu Jijun Zhao Key Laboratory of Materials Modification by Laser Ion and Electron Beams (Dalian University of Technology)Ministry of Education Institute for Superconducting and Electronic Materials (ISEM) University of Wollongong Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing Computational Science Research Center

Silicene has achieved rapid development due to its exotic electronic properties. Its low room-temperature mobility of 00 cm·Vs, however, inhibits device applications such as in field-effect transistors. Generally, defects would act as scattering centers and thus reduce the carrier mobility. In this paper, the morphologies of various point defects in epitaxial silicene on Ag(111) surfaces have been systematically investigated using first-principles calculations combined with experimental STM observations. The STM signatures for various defects in epitaxial silicene on Ag(111) surface are identified. In particular, the formation energies of point defects in Ag(111)-supported silicene sheets show an interesting dependence on the superstructures, which, in turn, may have implications for controlling the defect density during the synthesis of silicene. Through estimating the concentrations of various point defects in different silicene superstructures, the defective appearance of (13) × (13) silicene in experiments is explained.

关键词： silicene point defects STM

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Journal of Materials Science & Technology 2023年第7期138卷 50-58页

作者： Dongliang Su Jiahui Cheng Shan Li Shengnan Zhang Tu Lyu Chaohua Zhang Junqin Li Fusheng Liu Lipeng Hu College of Materials Science and Engineering Shenzhen Key Laboratory of Special Functional MaterialsGuangdong Research Center for Interfacial Engineering of Functional MaterialsGuangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and UtilizationInstitute of Deep Earth Sciences and Green EnergyShenzhen UniversityShenzhen 518060China Superconducting Materials Research Center Northwest Institute for Nonferrous Metal ResearchXi’an 710016China

To date,the benchmark Bi_(2)Te_(3)-based alloys are still the only commercial material system used for ther-moelectric solid-state ***,the conspicuous performance imbalance between the p-type Bi_(2-x)Sb_(x)Te_(3)and n-type Bi_(2)Te_(3-x)Se_(x) legs has become a major obstacle for the improvement of cooling devices to achieve higher *** our previous study,novel n-type Bi_(2-x)Sb_(x)Te_(3)alloy has been pro-posed via manipulating donor-like effect as an alternative to mainstream n-type Bi_(2)Te_(3-x)Se_(x).However,the narrow bandgap of Bi_(2-x)Sb_(x)Te_(3)provoked severe bipolar effect that constrained the further improvement of zT near room ***,we have implemented band gap engineering in n-type Bi_(1.5)Sb_(0.5)Te_(3)by employing isovalent Se substitution to inhibit the undesired intrinsic excitation and achieve the dis-tinguished room-temperature ***,the preferential occupancy of Se at Te^(2)site appropriately enlarges the band gap,thereby concurrently improving the Seebeck coefficient and depressing the bipolar thermal *** addition,the Se alloying mildly suppresses the compensation mechanism and essentially preserves the already optimized carrier concentration,which maintains the peak zT near room ***,the large strain field and mass fluctuation generated by Se alloying leads to the remark-able reduction of lattice thermal ***,the zT value of Bi_(1.5)Sb_(0.5)Te_(2.8)Se_(0.2)reaches 1.0 at 300 K and peaks 1.1 at 360 K,which surpasses that of most well-known room-temperature n-type thermoelectric *** results pave the way for n-type Bi_(2-x)Sb_(x)Te_(3)alloys to become a new and promising top candidate for large-scale solid-state cooling applications.

关键词： Thermoelectric Bi_(2)Te_(3) Band gap Bipolar effect point defects

Solvent induced shape change in CePO_4:Dy^(3+) nanophosphors and effect of metal ions: A photoluminescence study

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Journal of Rare Earths 2012年第12期30卷 1217-1224页

作者： Reena Okram N.Rajmuhon Singh Department of Chemistry Manipur University

The influence of different solvents and metal ions （Li^＋, Ba^2＋, Bi^3＋） on the crystallization behaviour, morphology and enhancement in photoluminescence intensity of Dy^3＋ doped CePO4 were investigated. Highly crystalline luminescent nanophosphors of CePO4：DY^3＋ re-dispersible in polar solvents were successfully prepared via a simple polyol route at 140 ℃. As-prepared Dy^3＋ doped CePO4 nanophosphors prepared in EG and DMF appeared to have crystalline monoclinic phase but exhibited hexagonal phase when prepared in water and water mixed solvents, The hexagonal phase transformed to monoclinic phase after heating at 900 ℃. TEM study revealed different shapes of the synthesized nanophosphors with change of solvents. The luminescence intensity of 4F9/2→6H15/2 at 478 nm （blue） was found to be more prominent than 4F9/2→6H13/2 at 572 nm （yellow）. The introduction of metal ions （Li＋, Ba2＋ and Bi3＋） in CePO4：Dy3＋ led to considerable luminescent enhancement. The nanophosphors were subsequently incorporated in polymer films of PVA which showed the characteristic emissions of Dy3＋. It also served as an effective method to improve the performance of polymer materials and brought about novel properties in them.

关键词： enhanced luminescence rare earth point defects nanophosphor re-dispersible