A narrow-base transistor with one-base contact is designed for digital IC application. Formed by all ion implantation on a p-type Si wafer, the npn transistor has a base width about 80-100 nm and the carrier concentration is 1018cm-3. The base is biased by voltage signals. When Vbe, is about 1. 2 V, βac(△Ic/△Ib)= 2. 5, gmac(△Ic/ △Vbe,) = 0. 4 mS and gmac/gm is much higher than βac/β. The transistor can be accurately characterized by its gm. This type of transistor tends to be a voltage-controlled device, and so it is suitable for digital IC's. A toggle circuit is made using the device and the flip-flop is realized by controlled voltage.

A newly structured transistor with one-base contact is designed. This npn transistor's structure is formed fully by ions implantation on a p-type wafer, the base width is about 80 nm and the carrier concentration is 1018 cm-3. The transistor is fabricated on a 2 μm laboratory line. The base is biased by voltage signals, and when Vbe is about 1.15 V, βac (ΔIc/ΔIb)=2.7, gmac (ΔIc/ΔVbe)=0.45 mS. gmac/gm is far higer than βac/β. Therefore the transistor can be characterized or described accurately by its gm, and this type of transistor tends to be a voltage-controled device, and can be used in digital circuits.

Device physics and integrated device and circuit simulation of "dual carrier field effect transistor" (DCFET) with effective channel length of 5-30nm had been presented in C. Huang et al. (2004). Two dimensional approximation methods had been used in these studies. Recently, two dimensional exact numerical simulations had been carried out for mesa type SOI switching "vertical dual carrier field effect transistor" (VDCFET). This exact method is presented in this paper briefly. More details are reported in R. Yang (2004). The comparison of the simulation results of the approximate physical method and of the exact numerical method shall be discussed and are shown to be in good agreement. Based on these simulation results, mesa type SOI switching VDCFET with effective channel of 30nm was designed and fabricated by using ion implantation processes. These fabrication processes shall be presented. The measured d.c. characteristics shall be presented and they are in good agreement with the device simulation results

The structural, superconducting and magnetic properties of La2Cu1-xZnxO4+delta (0 less than or equal to x less than or equal to 0.1) chemically oxidized by NaClO at room temperature were studied. All the samples before and after oxidation are single phase with orthorhombic structure, as indicated by their powder X-ray diffraction analysis. The iodometric titration results indicate that Zn-substituted La2Cu1-xZnxO4 is more favorable for the insertion of the excess oxygen, as compared to the Zn-free La2CuO4. The T-c suppression rate resulting from Zn substitution in La2Cu1-xZnxO4+delta is -2.4 K/%. The effective magnetic moment induced by the non-is magnetic Zn ion is the order of one Bohr magneton, which decreases with increasing the Zn concentrations in the range examined. The latter two results are qualitatively well consistent with those obtained in La2-xSrxCu1-yZnyO4 with the Sr optimal doping. This reveals that the non-magnetic Zn ions play the same role in both of the La2Cu1-xZnxO4+delta with the excess oxygen content of about 0.1 and the La2-xSrxCu1-yZnyO4 with the Sr optimal doping. (C) 2003 Elsevier Ltd. All rights reserved.

Within the framework of effective mass approximation, we have calculated the electronic structure of the two laterally coupled quantum dots with a donor by the finite element method. The calculated results show that the bond states of quantum-dot molecules are quite sensitive to the donor positions. By varying the donor position, the transition from covalent to ionic bond state is realized for some electronic states. Some extreme cases are also discussed for comparison.

采用三点哈巴德模型及弗洛盖定理,研究了交变电场驱动下线形三量子点分子中双电子的动力学行为.由于系统哈密顿量中不包含自旋反转项,所以系统单态和三重态子空间是完全解耦的,可以分开进行讨论.研究表明,自旋三重态九维子空间还可以进一步分解成三个不相耦合的子空间,在每一个子空间中,动力学行为与交变电场驱动的双量子点中双电子的动力学行为相似.对自旋单态6维子空间,数值计算还表明,在合适的外加交变电场驱动下,电子在量子点之间的隧穿被抑制,初始局域在一个量子点中的两个电子能够在一定时间内保持其局域状态.

In this Letter we study the dynamical behaviors of an exciton confined in coupled quantum dots driven by an ac electric field. By integrating the time periodic Schödinger equation numerically, we find that the dynamics of the exciton can be manifestly divided into two regimes according to the amplitude of the electric field. In the strong field regime, the quantum tunneling of the exciton is strongly quenched when they are driven by a suitable ac field. Furthermore, the exciton can keep staying in their initial state for a short of time. However in the weak field regime, the exciton can be trapped in one of the dots when the ratio of field strength to the frequency is a root of Bessel function J0. In particular, the Coulomb interaction enhances the dynamical localization effect. By the perturbative method we obtain the solutions to the Floquet function, leading to more detailed understanding of these effects.

Using the three-site Hubbard model and Floquet theorem, we investigate the dynamical behaviors of two electrons which are confined in a line-shape three quantum dot molecule driven by an AC electric field. Because the Hamiltonian contains no spin-flip terms, the six- dimension singlet state and nine-dimensional triplet state sub-spaces are decoupled and can be discussed respectively. In particular, the nine-dimensional triplet state sub-spaces can also be divided into 3 three-dimensional state sub-spaces which are fully decoupled. The analysis shows that the Hamiltonian in each three-dimensional triplet state sub-space, as well as the singlet state sub-space for the no double-occupancy case, has the same form similar to that of the driven two electrons in two-quantum-dot molecule. Through solving the time-dependent Schödinger equation, we investigate the dynamical properties in the singlet state sub-space, and find that the two electrons can maintain their initial localized state driven by an appropriately ac-field. Particularly, we find that the electron interaction enhances the dynamical localization effect. The use of both perturbation analytic and numerical approach to solve the Floquet function leads to a detail understanding of this effect.

利用有效的两点Hubbard模型,研究了在高强度交变电场驱动下的双量子点分子中激子的动力学行为.利用微扰理论,求解Floquet方程,从而得到准能的解析解,表明准能随交变电场的变化出现一系列共振点.通过计算初始局域态随时间的演化,发现在这些共振点处,动态局域化能够建立起来,说明尽管驱动电场倾向于使电子和空穴在空间分离,但在合适的强外电场驱动与弱的量子点间的耦合作用下,初始局域态依旧可保持动态局域化.

With a two-site Hubbard model and Floquet theorem, we investigate the dynamic behaviour of an exciton confined in a coupled double-quantum-dot system driven by an alternating current(AC) electrical field. The calculation shows that the quasi-energy levels versus the amplitude of the external field undergo a series of exact-crossing and avoid-crossing. Generally, the initially localized state can remain forever at the first exact-crossing point of two ground quasi-energy levels. Increasing the interaction of the electron and hole, the degree of dynamical localization is enhanced. At the second exact-crossing point of ground quasi-energy levels, this kind of dynamical localization is decayed. At the point of avoid-crossing and offset from the exact-crossing, the dynamical localization ceases to maintain. This demonstrates the possibility to control the exciton states on extremely short time scales using the appropriate AC field with the adjustable amplitude and frequency, which may be useful for quantum information processing.

We discuss theoretically the transport of a light pulse along a quantum wire made of a nonlinear ionic crystal. Under the adiabatic approximation, the propagation of the axial component of the electric field along the quantum wire has soliton properties and its distribution in the cross section of the quantum wire still approximately satisfies the Bessel equation. The size effect of the quantum wire on the dispersion relation of the polaritons is also discussed.

采用两点Hubbard模型和Floquet定理研究了在交变电场驱动下双量子点分子中激子的动力学行为.数值计算表明,系统准能随交变电场振幅的变化会出现一系列严格交叉和回避交叉.在某些弱场区的准能交叉点处,初始局域在一个量子点的电子和空穴依旧保持其初始局域状态.特别是随着两粒子之间的库仑相互作用的增强,这种动态局域化程度也得到加强.在强场区准能交叉点处,激子的动态局域化也能够建立起来.应用微扰理论求解Floquet方程,得到准能的解析解,可更清晰地了解系统的这种动态局域化特性.

In this paper, we theoretically discuss the soliton properties of light pulse transportation on the surface of an ionic crystal having strong nonlinear interactions between ions of unit cells. We analyze in detail the dark solitons when the nonlinear coefficient g is positive and negative, respectively. It is found that whether the nonlinear coefficient g is positive or negative, the dark solitons can be formed over the whole dispersion relation area of surface polaritons considering nonlinear effects. Attention should be paid to the fact that around omega(TO), the light pulse can form advanced dark solitons, and there is a switching area from advanced dark soliton to retarded dark soliton near omega(TO). We also discuss the effects of higher nonlinear dispersion on the solitons.

We study the dynamics of two interacting electrons in a coupled-quantum-dot system with a time-dependent external electric field. The numerical results of the two-particle states reveal that the dynamical localization still exists under appropriate dc and ac voltage amplitudes. Such localization is different from the stationary localization phenomenon. Our conclusion is instructive for the field of quantum function devices.

An efficient and convenient oxidizing agent, sodium hypochlorite solution, has been used to chemically prepare the superconductor La2CuO4+δ at room temperature. The crystallographic data show an enhanced orthorhombic distortion and an increase of the unit-cell volume. The magnetic susceptibility properties reveal a sharp transition beginning at 45 K and the oxidized sample is a homogeneous and single-phase bulk superconductor. The iodometric titration measurements indicate that the oxidized sample has a higher excess-oxygen content of 0.11. Scanning electron microscope observations showed that no grain size difference was observed for the sample before and after oxidation.

采用有效质量近似和绝热近似,计算了量子阱中InAs/In1-xGaxAs自组织量子点(点在阱中,DWELL)的电子结构和光学性质. 结果表明,电子能级随受限势的增大而升高,并随着量子点的尺寸的增大而降低,而且量子阱的宽度和量子点浸润层的厚度增加也会导致能级有所降低. 说明DWELL结构参数变化会使光致发光峰发生相应的蓝移或红移.

在有效质量近似框架内 ,采用绝热近似 ,计算了在量子阱中GaN/AlxGa1-xN自组织量子点系统的电子结构和光学性质 .计算表明系统的电子能级随量子点受限势的增大而升高 ,随量子点尺寸的增大而降低 ,而且量子阱的宽度和量子点浸润层厚度的增加也会导致能级值有所降低 .说明结构参数会使在阱中的量子点的光致发光峰波长发生相应的蓝移或红移 ,与已知的实验结果一致 .

The scaling properties of the anisotropic nonlocal Kardar-Parisi-Zhang equation are studied by using scaling analysis method. The scaling exponents in both the weak-and strong-coupling regions are obtained. The exponents obtained in the weak-coupling region can well match the results of the dynamic renormalization-group analysis.

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