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electronic properties of hydrogen- and oxygen-terminated diamond surfaces exposed to the air

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Chinese Physics B 2009年第5期18卷 2041-2047页

作者：刘峰斌汪家道陈大融颜大运 State Key Laboratory of Tribology Tsinghua University

The electronic properties of hydrogen- and oxygen-terminated diamond surfaces exposed to the air are investigated by scanning probe microscopy （SPM）. The results indicate that for the hydrogen-terminated diamond surface a shallow acceptor above the valence-band-maximum （VBM） appears in the band gap. However, the oxygen-terminated diamond film exhibits a high resistivity with a wide band gap. Based on the density-functional-theory, the densities of states, corresponding to molecular adsorbate in hydrogenated and oxygenated diamond （100） surfaces, are studied. The results show that the shallow acceptor in the band gap for the hydrogen-terminated diamond film can be attributed to the interaction between the surface C H bonding orbitals and the adsorbate molecules, while for the oxygen-terminated diamond film, the interaction between the surface C-O bonding orbitals and the adsorbate molecules can induce occupied states in the valence-band.

关键词： hydrogen-termination oxygen-termination electronic properties diamond film

electronic properties of one-dimensional systems with long-range correlated binary potentials

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Chinese Physics B 2011年第8期20卷 335-339页

作者： Gong Long-Yan Tong Pei-Qing Zhou Zi-Cong College of Science Nanjing University of Posts and Telecommunications Nanjing 210003 China Department of Physics Nanjing Normal University Nanjing 210097 China Department of Physics Tamkang University 151 Ying-Chuan Tamsui 25137 Taipei Taiwan China

We study numerically the electronic properties of one-dimensional systems with long-range correlated binary potentials. The potentials are mapped from binary sequences with a power-law power spectrum over the entire frequency range, which is characterized by correlation exponent β. We find the localization length ζ increases withβ. At system sizes N →∞, there are no extended states. However, there exists a transition at a threshold ζ. Whenβ 〉 βc, we obtain ζ 〉 0. On the other hand, at finite system sizes, ζ≥ N may happen at certain β, which makes the system ＂metallic＂, and the upper-bound system size N＊（β） is given.

关键词： electronic properties long-range correlation binary potentials localization

First-Principles Study on the Stability and electronic properties of Bi-Doped Sr_3Ti_2O_7

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Journal of Materials Science & Technology 2018年第5期34卷 891-898页

作者： Yanli Lu Fang Liu Xiang Li Feng Gao Zheng Chen State Key Laboratory of Solidification Processing Northwestern Polytechnic University

The electronic and crystal structural properties of Bi-doped Sr3Ti2O7 are studied using the first principles density functional theory（DFT）based on pseudopotentials basis and plane-wave *** results show that the formation energy of Bi doping in Site-1 and Site-2 of Sr3Ti2O7 increases with increasing doping *** at the same doping concentration,the formation energy of Bi doping in Site-2 is lower than that in *** undoped Sr3Ti2O7is found to be an insulator and its Fermi level stays at the top of the valence *** the Fermi level of the Bi-doped Sr3Ti2O7moves into the bottom of conduction band,the system undergoes an insulator-to-metal phase ***,our calculation results demonstrated that the Fermi level of the Bi-doped Sr3Ti2O7goes deeper into the bottom of conduction band with increasing doping concentration.

关键词： Strontium titanate ceramics Bi-doping Phase stability electronic properties First-principles calculations

Structural, mechanical, electronic properties, and Debye temperature of quaternary carbide Ti3NiAl2C ceramics under high pressure: A first-principles study

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Chinese Physics B 2021年第3期30卷 416-422页

作者： Diyou Jiang Wenbo Xiao Sanqiu Liu Key Laboratory of Nondestructive Testing Ministry of EducationNanchang Hangkong UniversityNanchang 330063China Fujian Science&Technology Innovation Laboratory for Energy Devices of China(21C-LAB) Ningde 352100China Department of Physics Nanchang UniversityNanchang 330047China

Quaternary carbide Ti3NiAl2C ceramics has been investigated as a potential nuclear fusion structural material,and it has advantages in certain aspects compared with Ti2AlC,Ti3AlC2,and Ti3SiC2 structural *** this paper,quaternary carbide Ti3NiAl2C ceramics is pressurized to investigate its structural,mechanical,electronic properties,and Debye *** carbide Ti3NiAl2C ceramics still maintains a cubic structure under pressure(0–110 GPa).At zero pressure,quaternary carbide Ti3NiAl2C ceramics only has three bonds:Ti–Al,Ni–Al,and Ti–***,at pressures of 20 GPa,30 GPa,40 GPa,60 GPa,and 70 GPa,new Ti–Ni,Ti–Ti,Al–Al,Ti–Al,and Ti–Ti bonds *** the pressure reaches 20 GPa,the covalent bonds change to metallic *** volume of quaternary carbide Ti3NiAl2C ceramics can be compressed to 72%of its original volume at *** can improve the mechanical strength and ductility of quaternary carbide Ti3NiAl2C *** 50–60 GPa,its mechanical strength can be comparable to pure tungsten,and the material changes from brittleness to ***,the degree of anisotropy of quaternary carbide Ti3NiAl2C ceramics increases with the increasing *** addition,we also investigated the Debye temperature,density,melting point,hardness,and wear resistance of quaternary carbide Ti3NiAl2C ceramics under pressure.

关键词： quaternary carbide Ti3NiAl2C ceramics structural properties mechanical properties electronic properties Debye temperature first-principles

Effect of strain on structure and electronic properties of monolayer C_(4)N_(4)

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Chinese Physics B 2024年第5期33卷 595-600页

作者：陈昊徐瑛赵家石周丹 School of Physics Changchun University of Science and TechnologyChangchun 130022China School of Computer Science and Technology Changchun University of Science and TechnologyChangchun 130022China

The first-principles calculations are performed to examine structural,mechanical,and electronic properties at large strain for a monolayer C_(4)N_(4),which has been predicted as an anchoring promising material to attenuate shuttle effect in Li–S batteries stemming from its large absorption energy and low diffusion energy *** results show that the ideal strengths of C_(4)N_(4)under tension and pure shear deformation conditions reach 13.9 GPa and 12.5 GPa when the strains are 0.07 and 0.28,*** folded five-membered rings and diverse bonding modes between carbon and nitrogen atoms enhance the ability to resist plastic deformation of C_(4)N_(4).The orderly bond-rearranging behaviors under the weak tensile loading path along the[100]direction cause the impressive semiconductor–metal transition and inverse semiconductor–metal *** present results enrich the knowledge of the structure and electronic properties of C_(4)N_(4)under deformations and shed light on exploring other two-dimensional materials under diverse loading conditions.

关键词： two-dimensional materials strain effect structural evolution electronic properties

First principles study on geometric and electronic properties of two-dimensional Nb_(2)CT_(x) MXenes

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Chinese Physics B 2022年第3期31卷 504-510页

作者： Guoliang Xu Jing Wang Xilin Zhang Zongxian Yang Henan Key Laboratory of Photovoltaic Materials School of Physics Henan Normal UniversityXinxiang 453000China

MXenes are a new type of two-dimensional carbides with rich physical and chemical properties. The physics of MXenes, and thus the applications, are dominated by surface functional groups. Herein, the effects of different terminations(O,S, Se, Te) on the geometric and electronic properties of Nb_(2)C MXenes were studied via density functional theory(DFT)calculations. Three adsorption sites were examined to determine the most stable configurations. The results showed that both the types and the positions of surface functional groups influence the geometric stability and physical characters of Nb_(2)C. The S and Se terminations make the Nb_(2)C MXenes to be semiconductor, while Nb_(2)C MXenes with other terminations(O, Te) are conductor. The electron location function, density of states, Bader charge distribution, and the projected crystal orbital Hamilton population were conducted to explain the origin of adsorption stability and electronic nature difference. Our results provide a fundamental understanding about the effects of surface terminations on the intrinsic stability and electronic properties of Nb_(2)C MXenes.

关键词： Nb_(2)C MXenes surface functional groups geometric structure electronic properties

Structures and electronic properties of Mo_(2n)N_n(n=1-5):a density functional study

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Chinese Physics B 2010年第12期19卷 212-222页

作者：陈杭雷雪玲刘立仁刘志锋祝恒江 School of Mathematics Physics and InformaticsXinjiang Normal University

The lowest-energy structures and the electronic properties of Mo2nNn （n=1-5） clusters have been studied by using the density functional theory （DFT） simulating package DMol3 in the generalized gradient approximation （GGA）. The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mon （n = 2, 4, 6, 8, 10） clusters and nitrogen atoms which surround these cores. The average binding energy, the adiabatic electron affinity （AEA）, the vertical electron affinity （VEA）, the adiabatic ionization potential （AIP） and the vertical ionization potential （VIP） of Mo2nNn （n=1-5） clusters have been estimated. The HOMO LUMO gaps reveal that the clusters have strong chemical activities. An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.

关键词： Mo2nNn clusters density functional theory equilibrium structures electronic properties

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

First-principles study of electronic properties and stability of Nb_5SiB_2(001) surface

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Chinese Physics B 2011年第3期20卷 366-372页

作者：许昱江子尚家香王福合 Key Laboratory of Aerospace Materials and Performance(Ministry of Education) School of Materials Science and EngineeringBeihang University Department of Physics Capital Normal University

The density functional calculations are performed to study the electronic structure and stability of Nb5SiB2 （001） surface with different terminations. The calculated cleavage energies along the （001） planes in Nb5SiB2 are 5.015 J · m-2 and 6.593 J· m-2 with the break of Nb=Si and Nb-NbB bonds, respectively. There exists a close correlation between the surface relaxation including surface ripple and the cleavage energy： the larger the cleavage energy, the larger the surface relaxation. Moreover, the surface stability of the NbsSiB2 （001） with different terminations has been investigated by the chemical potential phase diagram. From a thermodynamics point of view, the four terminations can be stabilized under different conditions. In chemical potential space, NbB （Nb） and Nb （Si） terminations are just stable in a small area, whereas Si （Nb） and Nb （NbB） terminations are stable in a large area （the letters in brackets represent the subsurface atoms）.

关键词： first principles NbsSiB2 surface electronic properties surface stability