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1.
Copper-based delafossite oxides are excellent candidates for the p-type transparent conducting oxide (TCO), which is essential in realizing transparent semiconductor applications. Using angle-resolved photoemission spectroscopy (ARPES), we report the low-energy electronic structure of CuAlO2. We found that the band structure near the valence band top is characterized by hole bands with their maxima along the Brillouin zone boundary. Furthermore, the effective masses along the Γ–M and Γ–K directions were found to be (0.6 ± 0.1) m0 and (0.9 ± 0.1) m0, respectively, which impose an important benchmark against the existing band calculations. 相似文献
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Electronic and optical properties of 3N-doped graphdiyne/MoS2 heterostructures tuned by biaxial strain and external electric field 下载免费PDF全文
The construction of van der Waals (vdW) heterostructures by stacking different two-dimensional layered materials have been recognised as an effective strategy to obtain the desired properties. The 3N-doped graphdiyne (N-GY) has been successfully synthesized in the laboratory. It could be assembled into a supercapacitor and can be used for tensile energy storage. However, the flat band and wide forbidden bands could hinder its application of N-GY layer in optoelectronic and nanoelectronic devices. In order to extend the application of N-GY layer in electronic devices, MoS2 was selected to construct an N-GY/MoS2 heterostructure due to its good electronic and optical properties. The N-GY/MoS2 heterostructure has an optical absorption range from the visible to ultraviolet with a absorption coefficient of 105 cm-1. The N-GY/MoS2 heterostructure exhibits a type-Ⅱ band alignment allows the electron-hole to be located on N-GY and MoS2 respectively, which can further reduce the electron-hole complexation to increase exciton lifetime. The power conversion efficiency of N-GY/MoS2 heterostructure is up to 17.77%, indicating it is a promising candidate material for solar cells. In addition, the external electric field and biaxial strain could effectively tune the electronic structure. Our results provide a theoretical support for the design and application of N-GY/MoS2 vdW heterostructures in semiconductor sensors and photovoltaic devices. 相似文献
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运用密度泛函理论体系下的平面波赝势(PWP)和广义梯度近似(GGA)方法,利用第一性原理计算了不同压强下六方纤锌矿结构AlN晶体的晶格常数、总能量、电子态密度、能带结构、光反射系数与吸收系数。通过比较能带结构的变化行为,得出 AlN在16.7Gpa附近存在等结构相变,即由直接带隙结构转变为间接带隙结构。同时,结合高压下的态密度分布图和能级移动情况,分析了AlN在高压下的光学性质,吸收谱有向高能端移动(蓝移) 的趋势。 相似文献
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运用密度泛函理论体系下的平面波赝势(PWP)和广义梯度近似(GGA)方法,利用第一性原理计算了不同压强下六方纤锌矿结构AlN晶体的晶格常数、总能量、电子态密度、能带结构、光反射系数与吸收系数。通过比较能带结构的变化行为,得出 AlN在16.7Gpa附近存在等结构相变,即由直接带隙结构转变为间接带隙结构。同时,结合高压下的态密度分布图和能级移动情况,分析了AlN在高压下的光学性质,吸收谱有向高能端移动(蓝移) 的趋势。 相似文献
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采用基于第一性原理的线性缀加平面波方法(FP-LAPW),研究Al掺杂SnO2材料Sn1-xAlxO2 (x= 0,0.0625,0.125,0.1875,0.25)的电子结 构和光学性质,包括能带结构、电子态密度、介电函数和其他一些光学性质.计算结果表明,掺杂Al之后价带上部分折叠态增加,价带宽度发生收缩,对导带底起作用的Sn 5s态减少,使得带隙增宽,且态密度整体向高能方向发生移动.随着Al掺杂量的增加带隙越来越宽,Al杂质能级在导带部分与Sn 5p态电子相互作用逐渐增强,虚部谱中的第一介电峰的强度随掺杂Al浓度增大而减弱.同时,吸收谱及其他光学谱线与介电函数虚部谱线相对应,各谱线均发生蓝移现象,对应带隙增宽,从理论上指出了光学性质与电子结构之间的内在关系.
关键词:
能带结构
态密度
光学性质
介电函数 相似文献
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利用第一性原理计算了立方相萤石TiO2的晶胞参数,能带结构和电子态密度.结果显示萤石TiO2属于间接带隙半导体材料,其间接禁带宽度(Γ→X)Eg为2.07 eV,比常见的金红石和锐钛矿TiO2的禁带宽度窄.为了更清楚地了解萤石的光学性质,利用Kramers-Kronig色散关系,分别对萤石和金红石TiO2的复介电常数、吸收率等参数进行了计算,并将二者结果做了比较.其中萤石TiO2的静介电常数为8.31.金红石TiO2的静介电常数表现为各向异性ε1xy(0)=6.01和ε1z(0)=7.07,该计算结果与实验值一致.吸收光谱的对比结果显示萤石结构在51nm和153 nm处增加了新的吸收峰,并且吸收光谱范围已扩大到了可见光区. 相似文献
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The full regions of the electronic and optical properties of in-plane biaxial strained thin film ZnO are studied using pseudopotential plane-wave method. The fundamental band gap at the Γ point increase linearly with the increase of tensile strains, but decreased with the compressive ones. The strains affected the local tetrahedral symmetry, and so the splitting of crystal field energy. The band dispersion relation of the valence band maximum changes with the strains, which means the residual strains have effects on the effective hole mass, thus the transportation properties of the p-type ZnO. The changes tendency of optical properties up to full regions under strains have been shown and discussed. 相似文献
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We report on density functional theory (DFT) calculations of the total and partial densities of states of rubidium dilead pentabromide, RbPb2Br5, employing the augmented plane wave+local orbitals (APW+lo) method as incorporated in the WIEN2k package. The calculations indicate that the Pb 6s and Br 4p states are the dominant contributors to the valence band: their main contributions are found to occur at the bottom and at the top of the band, respectively. Our calculations reveal that the bottom of the conduction band is formed predominantly from contributions of the unoccupied Pb 6p states. Data of total DOS derived in the present DFT calculations are found to be in agreement with the experimental X-ray photoelectron valence-band spectrum of this compound. The predominant contributions of the Br 4p states at the top of the valence band of rubidium dilead pentabromide are confirmed by comparison on a common energy scale of the X-ray emission band representing the energy distribution of the valence Br p states and the X-ray photoelectron valence-band spectrum of the RbPb2Br5 single crystal. Main optical characteristics of RbPb2Br5, such as dispersion of the absorption coefficient, real and imaginary parts of dielectric function, electron energy-loss spectrum, refractive index, extinction coefficient and optical reflectivity are explored for RbPb2Br5 by the DFT calculations. 相似文献
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《Current Applied Physics》2014,14(9):1257-1262
A single phase of delafossite CuAlO2 (CAO) was successfully synthesized by a 600 W microwave radiation for 20 min. The CAO sample was composed of quite distorted single-crystalline plates with 200–350 nm thick. Its atomic vibrations were detected at 760 and 550 cm−1 belonging to Al–O and Cu–O stretching, respectively. The direct and indirect energy gaps were respectively determined to be 3.9 and 2.9 eV. The photoluminescence (PL) at room temperature was at 585 nm (2.12 eV) corresponding to the indirect energy gap and at 760 nm (1.63 eV) corresponding to the p-type native defect. For its thermoelectric (TE) properties, the Seebeck coefficient (S) was positive value, with holes as the majority of charge carriers. By increasing of the test temperature, both the electrical resistivity and absolute value of Seebeck coefficient were decreased, but the power factor was in the opposite manner. The dimensionless figure of merit (ZT) of the crystalline CAO was evaluated to be the maximum of 9 × 10−3 at 1073 K. 相似文献
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The electronic structures, optical and thermodynamic properties of orthorhombic UCoGe are investigated using the generalized gradient approximation (GGA) formalism in the framework of the density functional theory (DFT). The obtained lattice parameters, bulk modulus B and its pressure derivative B′ of UCoGe are in agreement with the available experimental data. From the analysis of band structure and density of states coming out from our calculations, we can see that UCoGe in the ground state belongs to a typical metallic alloy. Various optical properties, including the dielectric function and absorption coefficient as functions of the photon energy are calculated. The thermodynamic properties of UCoGe are predicted using the quasi-harmonic Debye model for the first time. The Debye temperature, the Grüneisen parameter, the heat capacity and the thermal expansion coefficient are obtained at high pressures and temperatures. 相似文献
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Electronic and magnetic properties of Mn-doped WSe2 monolyer subject to isotropic strain are investigated using the first-principles methods based on the density functional theory. Our results indicate that Mn-doped WSe2 monolayer is a magnetic semiconductor nanomaterial with strong spontaneous magnetism without strain and the total magnetic moment of Mn-doped system is 1.038μB. We applied strain to Mn-doped WSe2 monolayer from -10% to 10%. The doped system transforms from magnetic semiconductor to half-metallic material from −10% to −2% compressive strain and from 2% to 6% tensile strain. The largest half-metallic gap is 0.450 eV at −2% compressive strain. The doped system shows metal property from 7% to 10%. Its maximum magnetic moment comes to 1.181μB at 6% tensile strain. However, the magnetic moment of system decreases to zero sharply when tensile strain arrived at 7%. Strain changes the redistribution of charges and arises to the magnetic effect. The coupling between the 3d orbital of Mn atom, 5d orbital of W atom and 4p orbital of Se atom is analyzed to explain the strong strain effect on the magnetic properties. Our studies predict Mn-doped WSe2 monolayers under strain to be candidates for thin dilute magnetic semiconductors, which is important for application in semiconductor spintronics. 相似文献
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The electronic structures and optical properties of Cu2ZnSnS4 (CZTS) under in-plane biaxial strain were systematically investigated using first-principles calculations based on generalized gradient approximation and hybrid functional method, respectively. It is found that the fundamental bandgap at the Γ point decreases linearly with increasing tensile biaxial strain perpendicular to c-axis. However, a bandgap maximum occurs as the compressive biaxial strain is 1.5%. Further increase of compressive strain decreases the bandgap. In addition, the optical properties of CZTS under biaxial strain are also calculated, and the variation trend of optical bandgap with biaxial strain is consistent with the fundamental bandgap. 相似文献
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Electronic structure and optical properties of BiSI crystal were investigated by the full potential linearized augmented plane wave (FL-LAPW) method with density functional theory (DFT). The complex dielectric function and optical constants, such as optical absorption coefficient, refractive index, extinction coefficient, energy-loss spectrum and reflectivity, were calculated. The optical properties of BiSI crystal were studied experimentally by spectroscopic ellipsometry. The experimental results were compared with the theoretical spectra of complex dielectric functions and with the spectra of a pseudo-dielectric function (PDF). This method shows that experimental spectra consist of four Laurence lines sum. 相似文献
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V. V. Sobolev A. I. Kalugin I. V. Vostrikov V. Val. Sobolev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(1):48-57
Spectra for the sets of optical functions for lead chloride are obtained for polarizations E ‖ a and E ‖ b at 10 K in the range of 4 to 30 eV. The calculations are carried out using synchrotron reflectivity spectra and a software package. The main features of the spectra of optical functions were established; they include the energies for volume and surface plasmons of two types. The bands and the spectra of permittivity and other optical functions for lead chloride crystals are calculated using the FP LAPW method. There was good agreement between the theoretical calculations and the data of the experimental spectra of R and other optical functions calculated using these R spectra. 相似文献
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V. G. Yarzhemskii M. A. Kazaryan E. N. Murav’ev 《Bulletin of the Lebedev Physics Institute》2012,39(9):254-256
Based on nonempirical calculations of the Au32 cluster, it is found that excited states from which only the quadrupole transition to the ground state is possible arise upon excitation of gold nanoparticles by photons with energies exceeding the minimum energy gap between occupied and vacant states. The possible role of such transitions in lasing of the nanoscale laser called the spaser is discussed. 相似文献
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二硒化钼的层间相互作用强,单层结构具有更低的带隙和更好的稳定性.由于独特的光学性质和优异的电学性能受到研究人员的广泛关注.本文基于密度泛函理论的第一原理,计算和分析了在双轴拉伸压缩应变条件下单层MoSe2能带结构,拉曼光谱和声子谱的变化规律以及性质产生的原因.在拉伸压缩应变作用下,直接带隙转变为间接带隙.当拉伸应变达到12%时,材料发生半导体-金属相变.当压缩应变达到6%时,声子谱中开始出现虚频率,表明结构开始变得不稳定. 相似文献