Different orbitals for different electrons in a system of intersecting quantum wires

The method of different orbitals for different spins is considered in the new context of ultrasmall, low-dimensional semiconductor structures. We solved the self-consistent wave equations for two interacting electrons in a quantum wire with a cross bar section. Such a quantum structure is of basic interest because one finds bound states in a potential that is classically open. The self-consistent solutions show that two electrons do not occupy one and the same bound state because orbital splitting is induced by Coulomb interactions. The state of one of the electrons becomes more squeezed while the other one appears delocalized because of screening effects from the first electron. Comparison is made with the Hylleraas' model for the orbital splitting in the helium atom. The effect of orbital splitting on electric transport is discussed briefly. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 667–673, 1997     

The use of biopolymer templates to fabricate low-dimensional gold particle structures

We report the current–voltage characteristics of gold nanoparticle–biopolymer networks at room temperature. The characteristics have features that are indicative of single-electron charging in ordered, one-dimensional chains of nanoparticles. From capacitance estimates and numerical simulations, we argue that the observed electrical behavior is related to the low size dispersion of the nanoparticles and the uniformity of the biopolymer lengths imbedded within the network.     

单电子晶体管的蒙特卡罗模拟及宏观建模(英文)

以单电子晶体管为研究对象,系统阐述了库仑阻塞、库仑台阶、单电子隧穿等物理现象的产生机理。微观模拟与宏观建模相结合,着重介绍了如何用蒙特卡罗方法和Matlab相结合对上述各种物理现象进行数值模拟,同时对单电子晶体管进行宏观电路等效,用一些常用元器件进行宏观建模。采用强大的模拟集成电路软件Hspice进行分析模拟,大大减少了计算及仿真时间。通过分析比较,两者曲线得到了较好的吻合,直观地反映了单电子晶体管的电学特性,为进一步研究复杂系统提供了理论依据。     

The effect of confinement on the electron thermal conductance of a nanocrystal

Coulomb blockade oscillations are found in the electron thermal conductance of a quantum dot (nanocrystal) in the regime of weak coupling with two electrode leads that is calculated within a linear response theory. An analytical expression is obtained in the quantum limit where electron level spacing is non-negligible. The effect of confinement on the electron thermal conductance is thereby explicitly shown. It is shown that in the quantum limit the periodicity of the Coulomb-blockade oscillations of the electron thermal conductance is the same as of the conductance. The shape and the magnitude of the electron thermal conductance depend explicitly on the temperature and the energy level spacing. It is found that the electron thermal conductance decreases nearly exponentially with increasing confinement and decreasing temperature.     

Symmetrical field effect and slow electron relaxation in granular aluminium

Conductivity and field effect measurements in thin insulating Al granular films are reported. The occurrence of a symmetrical field effect and of very slow conductance relaxations is demonstrated. They are identical to the electron glassy behaviours already reported in insulating indium oxide thin films. The results suggest that the phenomena are quite general. The study of structurally discontinuous samples should help to understand the origin and mechanism of the glassy behaviour. Received 4 December 2002 / Received in final form 26 February 2003 Published online 11 April 2003 RID="a" ID="a"e-mail: thierry.grenet@grenoble.cnrs.fr     

Quantum entanglement formation by repeated spin blockade measurements in a spin field-effect transistor structure embedded with quantum dots

We propose a method of operating a quantum state machine made of stacked quantum dots buried in adjacent to the channel of a spin field-effect transistor (FET) [S. Datta, B. Das, Appl. Phys. Lett. 56 (1990) 665; K. Yoh, et al., Proceedings of the 23rd International Conference on Physics of Semiconductors (ICPS) 2004; H. Ohno, K. Yoh et al., Jpn. J. Appl. Phys. 42 (2003) L87; K. Yoh, J. Konda, S. Shiina, N. Nishiguchi, Jpn. J. Appl. Phys. 36 (1997) 4134]. In this method, a spin blockade measurement extracts the quantum state of a nearest quantum dot through Coulomb blockade [K. Yoh, J. Konda, S. Shiina, N. Nishiguchi, Jpn. J. Appl. Phys. 36 (1997) 4134; K. Yoh, H. Kazama, Physica E 7 (2000) 440] of the adjacent channel conductance. Repeated quantum Zeno-like (QZ) measurements [H. Nakazato, et al., Phys. Rev. Lett. 90 (2003) 060401] of the spin blockade is shown to purify the quantum dot states within several repetitions. The growth constraints of the stacked InAs quantum dots are shown to provide an exchange interaction energy in the range of 0.01–1 meV [S. Itoh, et al., Jpn. J. Appl. Phys. 38 (1999) L917; A. Tackeuchi, et al., Jpn. J. Appl. Phys. 42 (2003) 4278]. We have verified that one can reach the fidelity of 90% by repeating the measurement twice, and that of 99.9% by repeating only eleven QZ measurements. Entangled states with two and three vertically stacked dots are achieved with the sampling frequency of the order of 100 MHz.     

单电子晶体管研究进展

在简单介绍了单电子晶体管 (SET)的工作原理后 ,综述了 SET在制造和应用方面的研究进展。     

基于微芯片的透射电子显微镜的低温纳米精度电子束刻蚀与原位电学输运性质测量

利用微芯片制备技术制备了带有电极的原位电学薄膜芯片,并结合自制的原位透射电镜样品台,实现了低温下透射电子显微镜聚焦电子束对InAs纳米线的精细刻蚀以及不同温度下的原位电学性能测量.研究发现,随着刻蚀区域截面积的减小,纳米线的电导率也随之减小.当纳米线的截面积从大于10000 nm2刻蚀至约800 nm2时,纳米线电导的减小速率与截面积的减小具有线性关系.同时利用低温聚焦电子束刻蚀,在InAs纳米线上原位制备了一个10 nm的纳米点,并在77与300 K下对该纳米点进行了电学性能测量.通过测量发现在77 K时出现库仑阻塞效应,发生了电子隧穿现象;而300 K时,热扰动提供的能量使这种现象消失.     

Temperature-sensitive asymmetrical bipolar resistive switches of polymer:nanoparticle memory devices

The interface between two bulk electronic materials can significantly affect the electrical behavior of electronic devices. But the interface between a bulk metal and metal nanoparticles has been rarely explored. This paper reports significant temperature effect on the asymmetrical resistive switches of polymer:nanoparticle memory devices. The devices have architecture of a polystyrene layer admixed with gold nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Au and Al electrodes. The devices exhibit significant resistive switches at room temperature. However, the resistive switches become less significant at temperature below 200 K, and they are not noticeable at 103 K. The temperature effect suggests that the resistive switches are assisted by the thermal energy. The charge transport through the devices has different mechanisms at high and low temperatures. At temperature above 220 K, the Poole–Frenkel emission is an important mechanism for the charge transport. At temperature below 220 K, the temperature-independent Fowler–Nordheim tunneling becomes an important process.