共查询到19条相似文献,搜索用时 125 毫秒
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本文计算了Heusler合金Li2AlGa和Li2AlIn的晶格参数、体积模量、体积模量的一阶导数、 电子能带结构、声子色散曲线和声子态密度,并与密度泛函理论中的广义梯度近似计算结果进行比较. 计算的晶格参数与文献有很好的一致性. 两个Heusler合金的电子能带结构表明它们是半金属结构. 并利用声子色散曲线和声子密度图研究Heusler合金晶格动力学. Li2AlGa和Li2AlIn Heusler合金在基态呈现动力学稳定. 相似文献
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本文运用第一性原理研究了FeN3掺杂扶手椅型和锯齿型石墨烯纳米条带的电子结构和输运性质. 结果表明,FeN3掺杂可导致两种类型的条带的能带结构发生显著变化,导致体系具有稳定的室温铁磁基态. 但是,只有扶手椅型条带具有明显的负微分电导和极强的电流极化效应(接近100%). 这是由于FeN3掺杂引入孤立的两条自旋向下能级,导致极强的电流极化. 同时,它们与自旋向下的不同子能带的耦合强度完全不同,导致体系呈现出负微分电导行为. 结果说明,通过FeN3掺杂扶手椅型石墨烯纳米条带也可用于制备自旋电子学器件. 相似文献
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利用高精度的CASSCF和MS-CASPT2电子结构计算方法系统地研究了2-(2'-羟基苯基)-4-甲基噁唑的光物理和光化学机理. 在CASSCF级别,首先优化得到势能面极小结构和圆锥交叉结构,及激发态质子转移、异构化、和失活的极小能量路径. 然后用MS-CASPT2方法对所有得到的结构和能量路径进行单点能量校正,我们发现在含有OH…N氢键的构象异构体中,激发态质子转移基本上是一个无垒的过程;在含OH…O 氢键的构象异构体中,激发态质子转移被抑制了. 此外,找到两个能量较低的酮式S1/S0圆锥交叉结构,使得激发态质子转移生成的S1酮式结构可以很快失活到达基态. 但是,醇式S1/S0圆锥交叉结构能量较高,抑制了S1醇式结构的激发态失活. 相似文献
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The electronic and magnetotransport properties of conduction electrons in the grain boundary interface of p-type Hg1−xCdxTe bicrystals are investigated. The results clearly demonstrate the existence of a two-dimensional degenerate n-type inversion layer in the vicinity of the grain boundary. Hydrostatic pressure up to 103 MPa is used to characterize the properties of the two-dimensional electron gas in the inversion layer. At atmospheric pressure three series of quantum oscillations are revealled, indicating that tthree electric subbands are occupied. From quantum oscilations of the magnetoresistivity
the characteristics parameters of the electric subbands (subband populations nsi, subband energies EF−Ei, effective electron masses m*ci) and their pressure dependences are established. A strong decrease of the carrier concentration in the inversion layer and of the corresponding subband population is observed when pressure is applied A simple theoretical model based on the triangular-well approximation and taking into account the pressure dependence of the energy band structure of Hg1−xCdxTe is use to calculate the energy band diagram of the quantum well and the pressure dependence of the subband parameters. 相似文献
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The measured parameters of spin-orbit spectral splitting in HgCdTe-based MIS structures with positive and negative Kane gap E g are compared with the parameters calculated using the three-and four-band Kane model. The disregard of the finite spin-orbit splitting Δ of the valence band in calculations leads to exaggerated values of Rashba splitting (especially for E g < 0) even for small ratios |E g|/Δ, although the subband parameters averaged over two spin branches of the spectrum in the two-, three-, and four-band Kane approximations for the same concentrations are practically identical. In the zero-gap HgCdTe, the measured as well as calculated values are noticeably higher, but the four-band approximation leads to values of splitting for both materials which are 20–40% lower than the experimental value. The inclusion of the interband interaction reduces these discrepancies, but does not eliminate them completely. It is shown that the approximations of the 2D spectrum with spin-orbit splitting linear in quasimomentum, which are conventionally used in the analysis, may lower the effective Rashba parameter by a factor of 2–4. 相似文献
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P.K. Basu 《Solid State Communications》1978,27(6):657-660
A Monte Carlo calculation of the drift velocity of hot electrons in quantized silicon inversion layers for (100)-oriented surface has been performed by considering the three lowest subbands. The intersubband and intervalley phonons conform to the surface Brillouin zone structure and are assumed to have bulk values of deformation potential constants. It is found that most of the electrons tend to occupy the E0′ subband at about 10 kV cm-1. The effect of surface-oxide-charge scattering is found to be quite important. The calculated curves show a change of slope at about 10 kV cm-1 and do not show clear saturation. This is in contrast with the experimental curve which shows first a smooth variation and then tends to saturate. 相似文献
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The interaction of conduction and valence bands in narrow gap semiconductors such as InSb and HgCdTe influences the position and width of subband energy levels in space-charge layers. While a nonzero width can only occur if electrons from the conduction band can tunnel into approximately degenerate states of the valence band the level shifts due to band mixing are always present. We present a Green's function treatment which allows in a simple way to discuss the dependence of band mixing effects on the parameters of thek·p-Hamiltonian in particular the band gap. The essential qualitative feature of the level shifts is adecrease of subband energy separation withdecreasing effective mass. This agrees with recent experimental results for Hg1-x
Cd
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Te. 相似文献
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D.K Ferry 《Surface science》1976,57(1):218-228
The momentum relaxation time for scattering of electrons in quantized levels of an inversion layer on a semiconductor surface is calculated for interactions via optical and intervalley phonons. A selection rule is found which prohibits transitions between subbands belonging to the same valley or set of valleys, at least in the zero order to which these scattering processes may occur. Relaxation times for the zero-order interaction and the first-order interaction are obtained for intervalley phonons. The results are applied to the case of a (100)-silicon surface, with electrons in the three lowest subbands (with energy levels E0, E1, E'0) of the two sets of valleys. Agreement with the experimental data of Fang and Fowler is good when the combined effects of intervalley and acoustic scattering are considered. 相似文献
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Reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy, and double-crystal X-ray curves showed that high-quality InAs quantum dot (QD) arrays inserted into GaAs barriers were embedded in an Al0.3Ga0.7As/GaAs heterostructure. The temperature-dependent photoluminescence (PL) spectra of the InAs/GaAs QDs showed that the exciton peak corresponding interband transition from the ground electronic subband to the ground heavy-hole subband (E1-HH1) was dominantly observed and that the peak position and the full width at half maximum corresponding to the interband transitions of the PL spectrum were dependent on the temperature. The activation energy of the electrons confined in the InAs/GaAs QDs was 115 meV. The electronic subband energy and the energy wave function of the Al0.3Ga0.7As/GaAs heterostructures were calculated by using a self-consistent method. The electronic subband energies in the InAs/GaAs QDs were calculated by using a three-dimensional spatial plane wave method, and the value of the calculated (E1-HH1) transition in the InAs/GaAs QDs was in reasonable agreement with that obtained from the PL measurement. 相似文献
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The subband dispersions in the Si(1 1 1) p-type inversion layers induced by Pb and Ga adsorbed surface structures were measured by angle-resolved photoemission spectroscopy (ARPES). The surface structures used here were and Si(1 1 1)6.3 × 6.3-Ga. is a new surface phase found in this study. Because it is significant in our study to investigate potential effects of surface superstructures on the hole subband dispersion, we investigated the subband energy levels quantitatively comparing them with those calculated using the triangular approximation. It was found that the energy separation of the adjacent subband quantum levels in the inversion layers induced by gallium adsorption does not follow the triangular approximation. The possible band bending shape was proposed to explain the quantum level spacing of the subbands in Ga-induced inversion layers. 相似文献
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S. Das Sarma 《Solid State Communications》1982,41(6):483-485
Electronic structure of the low lying quantized subbands is calculated for the electron accumulation layer on InP (100) system in a metal-insulator-semiconductor (MIS) structure. Hartree self-consistent technique at an arbitrary temperature has been used, neglecting many-body effects. In contrast to Si MIS system, a second subband is found to be populated even at low temperatures and moderate densities. Excitation energy, E10, is found to be about 30–40 meV in the temperature range 0–300 K at an electron density of 1012 cm?2. 相似文献
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Qi-Jun Liu Zheng-Tang LiuJi-Chao Chen Li-Ping FengHao Tian Wei Zeng 《Applied Surface Science》2012,258(8):3455-3461
Structural, electronic and chemical bonding properties of the (0 0 1) surface of cubic SrHfO3 have been investigated with both SrO and HfO2 termination using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory. The relaxed structures of two slabs have been analyzed, which shows the interplanar distance of two slabs has the same changed trend. The electronic band structures and density of states of two slabs have been discussed, showing the reduced band gaps by comparison with those of bulk system. The chemical bonding between Sr and O between the surface layer and subsurface layer as well as Hf and O has been increased. The surface energy, work function and stability have been calculated, which indicates SrO-terminated slab is more stable. 相似文献