Anomalous electric-field effect and glassy behaviour in granular aluminium thin films: electron glass?

We present a study of non-equilibrium phenomena observed in the electrical conductance of insulating granular aluminium thin films. An anomalous field effect and its slow relaxation are studied in some detail. The phenomenology is very similar to the one already observed in indium oxide. The origin of the phenomena is discussed. In granular systems, the present experiments can naturally be interpreted along two different lines. One relies on a slow polarisation in the dielectric surrounding the metallic islands. The other one relies on a purely electronic mechanism: the formation of an electron Coulomb glass in the granular metal. More selective experiments and/or quantitative predictions about the Coulomb glass properties are still needed to definitely distinguish between the two scenarios.     

3ω方法及其在纳米材料器件表征中的应用

阐明了3ω方法的机理，并在此基础上讨论了它的一些基本应用.利用3ω方法可以对具有优 良导热和导电能力的材料的热导率和热容进行测量；对不能导电的材料，固态的或液态的， 利用3ω方法能对它们的热导率进行测量.对测量中涉及到的热辐射问题的讨论表明，由于使 用的是小样品，热辐射造成的影响可以忽视.通过理论推导，使用二维隧穿结点阵并借助3ω 方法，可以给出一种性能良好的二维库仑阻塞测温法. 关键词： 3ω方法 热容（定压） 热导率 库仑阻塞     

Eliminating interactions between non-neighboring qubits in the preparation of cluster states in quantum molecules

We propose a scheme to eliminate the effect of non-nearest-neighbor qubits in preparing cluster state with double-dot molecules. As the interaction Hamiltonians between qubits are Ising-model and mutually commute, we can get positive and negative effective interactions between qubits to cancel the effect of non-nearest-neighbor qubits by properly changing the electron charge states of each quantum dot molecule. The total time for the present multi-step cluster state preparation scheme is only doubled for one-dimensional qubit chain and tripled for two-dimensional qubit array comparing with the time of previous protocol leaving out the non-nearest-neighbor interactions.     

Influence of the thickness of the tunnel layer on the charging characteristics of Si nanocrystals embedded in an ultra-thin SiO2 layer

In this paper, we have studied the effect of the thickness of the initial SiO₂ layer (5–7 nm) on the charge and discharge properties of a 2D array of Si nanoparticles embedded in these SiO₂ layers fabricated by ultra-low-energy ion implantation (ULE-II) and annealing. The structural characteristics of these nanocrystal-based memories (position of the nanocrystals with respect to the electrodes, size and surface density of the particles in the plane) were studied by transmission electron microscopy (TEM) and energy filtered TEM (EF-TEM). Electrical characterizations were performed at room temperature using a nano-MOS capacitor to be able to address only a few nanoparticles (nps). EFTEM gives the measurements of oxide thickness, injection, control and nps distances, size and density. I–V and I–t measurements exhibit current peaks and random telegraph signal fluctuations that can be interpreted as due to quantized charging of the nps and to some electrostatic interactions between the trapped charges and the tunnelling current. We have shown that these characteristics strongly vary with the initial oxide thickness, exhibiting several charging/discharging events for the 7-nm-thick layer while charging events prevail in the case of 5-nm-thick layer. These results indicate that the probability of discharging phenomena is reduced when the tunnel layer thickness decreases.     

Current and shot noise in two capacitively coupled single electron transistors with an atomic sized spacer

The currents and their fluctuations in two capacitively coupled single electron transistors are determined in the limit of sequential tunnelling. Our considerations are restricted to the case when the islands (dots) of the transistors are atomic-sized, which means each of them has only one single electronic level available for the tunnelling processes. The Coulomb interactions of accumulated charges on the both single electron transistors lead to the effect of the negative differential resistance. An enhancement of the current shot-noise was also found. Spectral decomposition analysis indicated the two main contributions to the shot-noise: low- and high-frequency fluctuations. It was found that the low frequency fluctuations (polarization noise) are responsible for a strong enhancement of the current noise. Received 9 October 2001 / Received in final form 8 March 2002 Published online 9 July 2002     

单电子晶体管-金属氧化物半导体场效应晶体管多峰值负微分电阻器件

传统的共振隧穿二极管的多峰值负微分电阻器件的峰值数目受到限制，由单电子器件和传统的金属氧化物半导体场效应晶体管(MOSFET)器件组成的多峰值负微分电阻器件在原理上具有无穷多个峰值，并且MOSFET使单电子晶体管(SET)的峰值和谷值电流大小受其源漏电压的影响减小.利用这种多峰值负微分电阻器件实现了多值存储器，该存储器原理上是无穷多值的.并且利用它的折叠的I-V特性，实现了一个4位的Flash A/D转换器，与传统的Flash A/D转换器相比，SET-MOSFET的A/D转换器大大地简化了电路. 关键词： 库仑阻塞 库仑振荡 负微分电阻 多值存储器     

单电子晶体管

由电子束纳米微刻技术制成的单电子晶体管呈现了新的物理现象：单电子隧穿效应和电荷宇称效应．这些发现为创造新型的电子器件开辟了光明前景，包括可以用比最基本电荷ｅ还小的电荷量来调制电流，处理以单电子为单位的电脑数字信息，并且也可发展成高度灵敏的微波探测器．     

Current--voltage characteristics of an individual helical CdS nanowire rope

This paper studies the electronic transport in an individual helically twisted CdS nanowire rope, on which platinum microleads are attached by focused-ion beam deposition. The current-voltage （I - V） characteristics are nonlinear from 300 down to 60 K. Some step-like structures in the I - V curves and oscillation peaks in the differential conductance （dI/dV - V） curves have been observed even at room temperature. It proposes that the observed behaviour can be attributed to Coulomb-blockade transport in the one-dimensional CdS nanowires with diameters of 6-10 nm.     

Coulomb blockade in triangular lateral small-size quantum dots

An AlGaAs/GaAs lateral quantum dot of triangular shape with a characteristic size L<100 nm containing less than ten electrons was studied. Single-electron oscillations of the conductance G of this dot were measured at G<e²/h. When going from Ge²/h to G≈0.5e²/h, a decrease was found not only in the amplitude but also in the period of the oscillations. A calculation of the 3D-electrostatics demonstrated that this effect is due to a change in the dot size produced by control voltages.     

Interference and interactions in mesoscopic rings

We consider a mesoscopic ring connected to external reservoirs by tunnel junctions. The ring is capacitively coupled to an external gate electrode and may be pierced by a magnetic field. Due to strong electron–electron interactions within the ring the conductance shows Coulomb blockade oscillations as a function of the gate voltage, while Aharonov–Bohm interference effects lead to a dependence on the magnetic flux. The Hamiltonian of the ring is given by a Luttinger model that allows for an exact treatment of both interaction and interference effects. We conclude that the positions of conductance maxima as a function the external parameters can be used to determine the interaction parameter , and the shapes of conductance peaks are strongly affected by electron correlations within the ring.