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采用射频磁控溅射技术, 在不同温度下制备了N掺杂Cu2O薄膜.透射光谱分析发现, N掺杂导致Cu2O成为允许的带隙直接跃迁半导体, 并使Cu2O的光学禁带宽度增加.不同温度下沉积的薄膜光学禁带宽度Eg=2.52± 0.03 eV.第一性原理计算表明, N掺杂导致Cu2O的禁带宽度增加了约25%, 主要与价带顶下移和导带底上移有关, 与实验报道基本符合.N的2p电子态分布不同于O原子, 在价带顶附近具有较大的态密度是N掺杂Cu2O变成允许的带隙直接跃迁半导体的根本原因. 相似文献
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本文研究了Xe(6p[1/2]0, 6p[3/2]2, and 6p[5/2]2)原子在聚焦条件下的动力学过程. 激发能级的原子密度在聚焦条件下会显著地增加,因此两个高激发态原子之间的energy-pooling碰撞的概率也会增加. 这种energy-pooling碰撞主要有三种类型. 第一种类型为energy-pooling碰撞导致的电离. 一旦将激发激光聚焦,就可以从侧面的窗口观察到非常明显的电离现象,不论激发能级是6p[1/2]0、6p[3/2]2或6p[5/2]2能级. 这种电离的产生机理是energy-pooling电离或者一个Xe*原子再吸收一个光子产生电离. 第二种类型为跨越较大能极差的energy-pooling碰撞. 当激发能级为6p[1/2]0能级的情况下,两个6p[1/2]0原子碰撞会产生一个5d[3/2]1原子和一个6s''[1/2]0原子. 第三种类型为跨越较小能级差的energy-pooling碰撞. 以5个二次产生的6p能级为上能级的荧光强度都变得更强,并且这些荧光的上升沿都变得更陡峭. 产生这些6p原子的主要机理是energy-pooling碰撞并非简单的碰撞弛豫. 基于理想气体原子之间的碰撞概率公式,推导出两个6p[1/2]0原子的energy-pooling碰撞速率为6.39x108s-1. 此外,6s原子在聚焦条件下的密度也会增加. 因此所有的荧光曲线会因为辐射俘获效应而出现非常严重的拖尾. 相似文献
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本文利用基于密度泛函理论(DFT)的第一性原理计算研究了它们的电子结构和光学性质.光学性质的计算结果和实验相一致.结果表明,Fe或Ag掺杂后,K2Ti6O13的带隙中出现了杂质带且其带隙值变小,因而使掺杂后的K2Ti6O13的吸收边发生红移并实现了其对可见光吸收.其中杂质带主要由Fe 3d态或Ag 4d态与Ti 3d态和O 2p态杂化而成.对于Fe掺杂的K2Ti6O13,杂质带位于带隙中间,因此可以作为电子从价带跃迁到导带的桥梁.对于Ag掺杂的K2Ti6O13,杂质带位于价带顶附近为受主能级,可以降低光生载流子的复合概率.实验和计算研究表明,通过Fe或Ag的掺杂可以实现了K2Ti6O13对可见光的吸收,这对进一步研究K2Ti6O13的光学性质具有重要意义. 相似文献
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近年来的理论和实验研究表明,通过不同离子共掺杂TiO2是减小其禁带宽度的一种有效方法.本文采用基于第一性原理的平面波超软赝势方法研究了C和Zn共掺杂TiO2的能带结构、态密度和光学性质.计算结果表明C-Zn共掺杂导致导带相对Fermi能级发生了明显的下降,同时在TiO2的导带下方与价带上方形成了新的杂质能级,使TiO2的禁带宽度变小, TiO2的光学吸收带边产生红移. 杂质能级可以降低光激发产生的电子-空穴对的复合概率, 提高TiO2的光催化效率. 此外, 掺杂后TiO2在可见光区的吸收系数有明显增加, 能量损失也明显减小. 相似文献
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运用第一性原理,对C掺杂锐钛矿相TiO2的电子结构进行了研究,从能带结构理论解释了C掺杂TiO2吸收光谱的一些实验现象.发现在C掺杂后的锐钛矿相TiO2的禁带宽度增大,并且在带隙中出现了杂质能级,这些杂质能级主要是由C 2p轨道上的电子构成的,它们之间是独立的,正是这些独立的杂质能级使TiO2掺杂后可以发生可见光响应.价带上的电子可以吸收一定能量的光子跃迁到杂质能级,而杂质能级上的电子也可以吸收一定能量的光子跃迁到导带,所以从理论上可以计算出掺杂后的TiO2在可见光范围内存在两个吸收边,与实验中所得到的现象相一致. 相似文献
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从双原子分子能级的物理表达式出发进行多次微分,建立了预测双原子分子体系R支高振转跃迁谱线的新解析公式. 使用新解析公式预测双原子体系R支高阶跃迁谱线的数据时,最多只需15条精确的实验跃迁谱线和该跃迁带中对应的上下 振动态的转动光谱常数B′v 和 B″v.将该解析公式用于预测Cl2+ 离子 A2∏u---X2∏g跃迁系(3,7)带和(4,8)带的跃迁谱线,不仅精确的重复了实验给出的较低阶的跃迁光谱数据值, 而且正确预言了所研究体系中缺失的振转跃迁谱线,尤其是高阶的跃迁谱线数据. 相似文献
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We have synthesized GaN-core/ZnO-shell nanowires and investigated effects of the ZnO coating. The X-ray diffraction pattern showed that as-synthesized samples are composed of GaN and ZnO. Transmission electron microscopy indicated that the deposited ZnO shell layer is poly-crystalline. The photoluminescence (PL) spectrum of GaN has been changed by the ZnO coating, where emission bands centered at roughly 1.9 eV, 2.5 eV, and 3.3 eV were newly added to the emissions from core GaN nanowires. We found that overall PL intensity has been significantly increased by coating the ZnO shell layers. 相似文献
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The electronic band structure and elastic constants of SnS2 and SnSe2 have been calculated by using density-functional theory (DFT). The calculated band structures show that SnS2 and SnSe2 are both indirect band gap semiconductors. The upper valence bands originate mainly from Sp and Snd electrons, while the lowest conduction bands are mainly from (S, Se) p and Sns states. The calculated elastic constants indicate that the bonding strength along the [100] and [010] direction is stronger than that along the [001] direction and the shear elastic properties of the (010) plane are anisotropic for SnS2 and SnSe2. Both compounds exhibit brittle behavior due to their low B/G ratio. Relationships among volumes, the heat capacity, thermal expansion coefficients, entropy, vibrational energy, internal energy, Gibbs energy and temperature at various pressures are also calculated by using the Debye mode in this work. 相似文献
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E. V. Bogdanov N. B. Brandt N. Ya. Minina S. S. Shirokov 《Moscow University Physics Bulletin》2011,66(6):568-573
The band structure, size quatized levels, and wave functions in the conduction and valence bands of strained n-Al
x
Ga1 − x
As/GaAs
y
P1 − y
/p-Al
x
Ga1 − x
As (y = 0.84) heterostructures are calculated numerically upon a uniaxial compression along the [110] direction. The calculation
indicates a sublinear increase of the effective optical gap in the GaAs0.84P0.16 quantum well, strong mixing of states of light and heavy holes, and merging of the corresponding ground states in the quantum
well of the valence band under a pressure of 4.5–5 kbar. The calculation of matrix elements of the electron-photon interaction
operator for a system of possible interband transitions permits one to determine the optical gain for the TE and TM modes.
The increase in this coefficient by two to fourfold under uniaxial compression agrees with the previously published experimental
data on the increase of the electroluminescence intensity. 相似文献
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C.E.T.Gonçalves da Silva 《Solid State Communications》1980,33(1):63-68
We study the magnetic susceptibility of FeSb2 within a model of highly correlated valence band states and conduction electrons Coulomb interaction. Inter-band Coulomb and Hund type couplings are also considered. The latter are strong due to the d character of both valence and conduction bands edges. We suggest that the high susceptibility of FeSb2(X ≈ 6×10?4emu/mole) may be further enhanced by the addition of selected impurities, leading to a magnetic ground state. 相似文献
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C. H. Jia Y. H. Chen X. L. Zhou A. L. Yang G. L. Zheng X. L. Liu S. Y. Yang Z. G. Wang 《Applied Physics A: Materials Science & Processing》2010,99(2):511-514
X-ray photoelectron spectroscopy has been used to measure the valence band offset of the ZnO/BaTiO3 heterojunction grown by metal-organic chemical vapor deposition. The valence band offset (VBO) is determined to be 0.48±0.09 eV,
and the conduction band offset (CBO) is deduced to be about 0.75 eV using the band gap of 3.1 eV for bulk BaTiO3. It indicates that a type-II band alignment forms at the interface, in which the valence and conduction bands of ZnO are
concomitantly higher than those of BaTiO3. The accurate determination of VBO and CBO is important for use of semiconductor/ferroelectric heterojunction multifunctional
devices. 相似文献
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x 《Superlattices and Microstructures》1996,19(4):251-261
The electronic structures of the zinc-blende GaN/Ga0.85Al0.15N compressively strained superlattices and quantum wells are investigated using a 6×6 Hamiltonian model (including the heavy hole, light hole and spin-orbit splitting band). The energy bands, wavefunctions and optical transition matrix elements are calculated. It is found that the light hole couples with the spin-orbit splitting state even at thek=0 point, resulting in the hybrid states. The heavy hole remains a pure heavy hole state atk=0. The optical transitions from the hybrid valence states to the conduction states are determined by the transitions of the light hole and spin-orbit splitting states to the conduction states. The transitions from the heavy hole, light hole and spin-orbit splitting states to the conduction states obey the selection rule Δn=0. The band structures obtained in this work will be valuable in designing GaN/GaAlN based optoelectronic devices. 相似文献
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The system zinc oxide/hexacyanoferrate was used to test the applicability of the theoretical model for electrochemical reactions at semiconductor electrodes based upon direct electron transfer between levels of equal energy. This model appears to be valid for electron transfer involving the conduction band. From the pH-dependence of the cathodic reactivity, a value of 0.75 eV is found for the rearrangement energy of Fe(CN)63?/Fe(CN)64?. This result, combined with capacity and potential data, allows the construction of a general energy scheme for the system under consideration. It is shown that direct electron transfer from filled redox levels to empty levels in the valence band is highly improbable, so that the observed hole capture by Fe(CN)64? from the UV-illuminated ZnO anode presumably occurs by a more complicated mechanism, e.g. involving surface states. 相似文献
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First-principles calculations, by means of the full-potential augmented plane wave method using the LSDA+U approach (local spin density approximation with Hubbard-U corrections), have been carried out for the electronic structure of the Al0.75Er0.25N. The LSDA+U method is applied to the rare-earth 4? states. We have investigated the electronic and magnetic properties.The Al0.75Er0.25N is shown to be a semiconductor, where the filled ? states are located in the valence bands and the empty ones above the conduction band edge. The magnetic interaction of the rare-earth ion with the host states at the valence and conduction band edges has been investigated and discussed. 相似文献
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Jorma Hölsä Marco Kirm Mika Lastusaari Janne Niittykoski Pavel Novák 《Journal of luminescence》2009,129(12):1560-1563
The electronic structures of the distrontium magnesium disilicate (Sr2MgSi2O7(:Eu2+)) materials were studied by a combined experimental and theoretical approach. The UV-VUV synchrotron radiation was applied in the experimental study while the electronic structures were investigated theoretically by using the density functional theory. The structure of the valence and conduction bands and the band gap energy of the material as well as the position of the Eu2+ 4f ground state were calculated. The calculated band gap energy (6.7 eV) agrees well with the experimental value of 7.1 eV. The valence band consists mainly of the oxygen states and the bottom of the conduction band of the Sr states. The calculated occupied 4f ground state of Eu2+ lies in the energy gap of the host though the position depends strongly on the Coulomb repulsion strength. The position of the 4f ground state with respect to the valence and conduction bands is discussed using the theoretical and experimental evidence available. 相似文献
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Electronic structure calculations were performed for substitutional erbium rare-earth impurity in cubic GaN using density-functional theory calculations within the LSDA+U approach (local spin-density approximation with Hubbard-U corrections). The LSDA+U method is applied to the rare-earth 4f states. The ErxGa1−xN is found to be a semiconductor, where the filled f-states are located in the valence bands and the empty ones above the conduction band edge. The filled and empty f-states are also shown to shift downwards and upwards in the valence and conduction bands, respectively, with increase in the U potentials. 相似文献