共查询到19条相似文献,搜索用时 165 毫秒
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应用密度泛函理论中的B3LYP方法计算并分析了不同生长模式下Bn(n= 2-15)团簇的几何结构及电子性质.同时,比较和讨论了不同生长模式下硼团簇的原子束缚能、能级间隙和第一电离势.研究表明:直线构型稳定性最低,金属性较强,尤其在n=8时能隙仅有0.061eV,说明该团簇已具有金属特征.平面或准平面构型稳定性最高,非金属性强.立体构型的稳定性与金属性介于直线和平面构型之间.另外,还讨论了基态团簇的束缚能、能量二阶差分、能级间隙和第一电离势随团簇尺寸的变化,结果表明B12与B14是幻数团簇. 相似文献
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运用散射矩阵方法,研究了台阶磁势垒量子结构中二维电子气的隧穿输运性质.结果表明:在零偏压下,电子传输概率的自旋极化曲线随入射能量的增加而振荡衰减;随着磁台阶数的增加,电子传输概率的自旋极化度最大值减小,同时电子传输概率的自旋极化度振荡衰减也越来越慢;随着磁台阶的总宽度增加,电子传输概率的自旋极化曲线出现更明显的振荡,电子隧穿磁台阶势垒表现出明显的量子尺寸效应;在偏置电压的作用下,电子传输概率的自旋极化度在宽广的入射能量区出现明显的振荡增大,电子隧穿磁台阶势垒表现出更明显的自旋过滤效应.
关键词:
磁台阶势垒
自旋极化
自旋过滤 相似文献
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在正统理论的基础上,提出了单电子三势垒隧穿结模型的主方程,并用线性方程组解法求出了其稳态解.通过数值模拟,得到了该系统的I-V特性曲线.发现其有别于双势垒隧穿结的情况,在传统库仑台阶的平台处曲线存在波纹状结构,分析得出这是由于第二个库仑岛上的电子数变化对I-V曲线的影响.此外,研究了各物理参数对I-V曲线的影响,发现三结系统可以降低对温度的要求,并应用Fermi能级处的能级间隔估算出出现库仑台阶现象的最高温度Tmax,为相关单电子器件的参数选择提供了理论依据.
关键词:
正统理论
库仑台阶
主方程
隧穿概率 相似文献
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在加速光晶格中玻色-爱因斯坦凝聚体(BEC),当同时考虑两体和三体相互作用时,其能级结构、隧穿率出现了独特的特性.在一维加速光晶格中的BEC,当两体和三体相互作用参数满足一定条件时,非线性两能级体系的能级结构中出现了圈结构,研究得出了圈的宽度随两体和三体相互作用参数变化的关系,并由此分析圈结构的出现及其大小对BEC隧穿率的影响. 相似文献
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研究了恒压应力下超薄栅氧化层n型金属-氧化物-半导体场效应晶体管(n-MOSFET)软击穿 后的导电机制.发现在一定的栅电压Vg范围内,软击穿后的栅电流Ig符合Fowl er-Nordheim隧穿公式,但室温下隧穿势垒b的平均值仅为0936eV,远小于S i/Si O2界面的势垒高度315eV.研究表明,软击穿后,处于Si/SiO2界 面量子化能级上的 电子不隧穿到氧化层的导带,而是隧穿到氧化层内的缺陷带上.b与缺陷带能 级和电 子所处的量子能级相关;高温下,激发态电子对隧穿电流贡献的增大导致b逐 渐降低.
关键词:
软击穿
栅电流
类Fowler-Nordheim隧穿
超薄栅氧化层 相似文献
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《Physics letters. A》2006,355(6):481-488
Resonant tunneling characteristics of triangular double-barrier diodes have been investigated systematically in this Letter, using Airy function approach to solve time-independent Schrödinger function in triangular double-barrier structures. Originally, the exact analytic expressions of quasi-bound levels and quasi-level lifetime in symmetrical triangular double-barrier structures have been derived within the effective-mass approximation as a function of structure parameters including well width, slope width and barrier height. Based on our derived analytic expressions, numerical results show that quasi-bound levels and quasi-level lifetime vary nearly linearly with the structure parameters except that the second quasi-level lifetime changes parabolically with slope width. Furthermore, according to our improved transmission coefficient of triangular double-barrier structures under external electric field, the current densities of triangular double-barrier diodes with different slope width at 0 K have been calculated numerically. The results show that the N-shaped negative differential resistance behaviors have been observed in current–voltage characteristics and current–voltage characteristics depend on the slope width. 相似文献
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Dynamics of the Dirac fermions, in particular the transmission coefficient and the resonant tunneling lifetime are studied across a bilayer graphene electrostatic double barrier structure modulated by an in plane homogeneous electric field. Asymmetric Fano type resonances are noted for the first time in the transmission spectrum of the bilayer graphene nanostructures and are found to be highly sensitive to the direction of incidence of the charge carriers and the applied homogeneous electric field. The effect of the external field on the extended and the evanescent modes is also analysed. Resonant tunneling lifetime is found to be highly anisotropic in nature. The chiral carriers are either accelerated or decelerated by the electric field depending on the energy of the quasi-bound states, the angle of incidence and the magnitude of the applied field. Effects of the external field on the localization of the chiral carriers are also discussed. 相似文献
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《Superlattices and Microstructures》2001,29(1):51-55
The effect of properly lined-up quantum-well (QW) states, under an external bias, on the electron resonant tunneling is investigated in an InAlAs/InGaAs triple-barrier structure. The degree of alignment of two QW confined ground states at a resonant voltage is analyzed with low-temperature measurement. The experimental data shows the enhanced resonant tunneling effects, and proves that the second QW structure added to the InGaAs/ InAlAs double-barrier heterostructure can act as an effective tool for probing and extracting the resonant tunneling properties deep in a QW. 相似文献
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《Superlattices and Microstructures》1995,17(1):35-39
Theoretical study of resonant tunneling is carried out in rectangular triple-barrier structures with C-type deep wells. Analytical expressions for the transmission coefficient and the resonance conditions are derived. Transmission characteristics versus electron energy are investigated and it is shown analytically that the transmission spectrum is a Lorentzian in form near energies of resonance. It is confirmed that the resonance energy is almost equal to the eigenenergy of the double-well structure. Moreover, wave functions of an electron at the resonance level are examined and the confining phenomenon is studied. 相似文献
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《Superlattices and Microstructures》1998,23(5):1047-1052
The enhanced electron tunneling effect and the electron Γ–X intervalley interlayer transfer in the AlAs/GaAs (001) triple-barrier heterostructure have been investigated both experimentally and theoretically. The effects of the external bias on the electronic structure, Γ–X state mixing and higher lying excited energy states are studied. The experimental observations show good agreement with the theoretical predictions based on the scattering theoretical approach of Green's function theory, which can handle electron interlayer intervalley propagation through the layered aperiodic heterostructure under the external bias. 相似文献
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《Superlattices and Microstructures》1994,15(4):373-376
We report an investigation of ballistic electron transport in GaAs/AlGaAs p-i-n single barrier structures with magnetic fields of up to 14T applied parallel to the tunneling direction (B//z). The energy distribution and relaxation processes of the non-equilibrium electron population injected into the p-doped collector from the Landau levels of the emitter accumulation layer are studied by means of electroluminescence (EL) spectroscopy. The observation of emitter Landau level structure in the ballistic electron EL spectra shows that the 2D to 3D tunneling process is elastic. In addition to the ballistic electron EL, cross-barrier recombination between the electron and hole accumulation layers is observed. This allows a precise determination of the initial energy distribution of the injected electrons. 相似文献
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We calculate the Hall conductivity sigma(xy) and resistivity rho(xy) of a granular system at large tunneling conductance g(T)>1. We show that in the absence of Coulomb interaction the Hall resistivity depends neither on the tunneling conductance nor on the intragrain disorder and is given by the classical formula rho(xy)=H/(n*ec), where n* differs from the carrier density n inside the grains by a numerical coefficient determined by the shape of the grains. The Coulomb interaction gives rise to logarithmic in temperature T correction to rho(xy) in the range Gamma less or similar T less or similar min(g(T)E(c), E(Th)), where Gamma is the tunneling escape rate, E(c) is the charging energy, and E(Th) is the Thouless energy of the grain. 相似文献
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A. B. Pashkovskii 《JETP Letters》2005,82(4):210-214
Expressions for resonance active high-frequency small-signal conductivity and resonance level widths have been derived for asymmetric triple-barrier resonance-tunneling structures with thin high barriers. It is found that if the levels forming a common resonance level have different parities in each of double-barrier structures, the width of the common level and, accordingly, the total conductance of the entire structure may increase manifold for a certain choice of the triple-barrier structure parameters. Consequently, the lifetime of electrons on this level also decreases drastically; hence, the conditions of coherent transport (departure of electrons from the structure without their collision with phonons) can be easily realized. 相似文献
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H. Kellay J. Rouch 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):121-129
In this paper we study the influence of the magneto-coupling effect between the longitudinal motion component and the transverse
Landau orbits of an electron on transmission features in single barrier structures. Within the parabolic conduction-band approach,
a modified one-dimensional effective-mass Schr?dinger equation, including the magneto-coupling effect generated from the position-dependent
effective mass of the electron, is strictly derived. Numerical calculations for single barrier structures show that the magneto-coupling
effect brings about a series of the important changes for the transmission probability, the above-barrier quasi-bound states,
and the tunneling time. Through examining the variation of the above-barrier resonant-transmission spectrum with the barrier
width and observing the well-defined Lorentzian line-shape of the above-barrier resonant peaks, we convincingly show that
the above-barrier resonant transmission in single barrier structures is delivered by the above-barrier quasibound states in
the barrier region, just as the below-barrier resonant tunneling in double barrier structures is mediated by the below-barrier
quasi-bound states in the well. Furthermore, we come to the conclusion that the magneto-coupling effect brings about not only
the splitting of the above-barrier quasi-bound levels but also the striking reduction of the level-width of the quasi-bound
states, correspondingly, the substantial increase of the density of the quasi-bound states. We suggest that magneto-coupling
effects may be observed by the measurements of the optical absorption spectrum associated with the above-barrier quasi-bound
states in the single barrier structures.
Received: 26 September 1997 / Revised: 26 November 1997 / Accepted: 15 December 1997 相似文献