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We present the local charge state modification at room temperature of small insulator-supported molecular ensembles formed by 1,1'-ferrocenedicarboxylic acid on calcite. Single electron tunnelling between the conducting tip of a noncontact atomic force microscope (NC-AFM) and the molecular islands is observed. By joining NC-AFM with Kelvin probe force microscopy, successive charge build-up in the sample is observed from consecutive experiments. Charge transfer within the islands and structural relaxation of the adsorbate/surface system is suggested by the experimental data.

International audience; 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.

STM studies of passivated Au nanocrystals immobilised on a passivated Au(111) surface: ordered arrays and single electron tunneling

A scanning tunnelling microscope with a gold tip was used to create clusters and form nano-dots, lines and corrals on a clean stepped Si(111) surface by applying a series of bias pulses to the tip-sample tunnelling junction. Nano-dots with diameters as small as a few nm can be realized. By decreasing the distances between nano-dots, it is possible to create continuous nano-lines of a few nm wide and over a few hundred nm long, which can be used as connections between micro- and nano-electronic components. A nano-corral of about 40 nm in diameter formed by many Au dots of a few nm in diameter each was also created on the Si(111) surface. Single electron tunnelling effects through nano-dots were studied and it was found that `Coulomb staircases' can be observed in the I-V (current-voltage) curve at room temperature through an Au tip-Au cluster-Si substrate double junction system.

The notion of quantum-dot cellular automata (QCA) as a possible replacement paradigm for conventional transistor-based logic is reviewed. Experiments using metal tunnel structures demonstrating a functional QCA cell are presented. It is shown that single electron tunnelling transistors used as electrometers verify proper switching of the QCA cell. Additionally, we provide evidence for a QCA cell switching frequency of 14 MHz, and a calculated upper limit of more than 5 GHz.

A single-electron tunnelling (SET) device consisting of a double junction and an environmental impedance is considered. Current-voltage characteristics are calculated using a self-consistent treatment of the environmental impedance. It is observed experimentally that Coulomb gaps become wide for large environmental resistances, which is in agreement with the theory. This modulation of the Coulomb gap by the environmental resistance can be a new operation principle of SET devices.

Current-transport properties of extremely thin composite films of and (about 9 to 15 nm in thickness) were studied. The observation of the sample cross-section by high-resolution transmission electron microscopy revealed that only a few Ag (Au) nanocrystals exist across the films. In spite of the simple device structure (i.e. just sandwiching the granular film between Al electrodes) and very large electrodes , Coulomb blockade (CB) and Coulomb staircase (CS) structures have been clearly observed at low temperatures. As the temperature rose, the CB and CS structures smeared out and random telegraph signals due probably to a charge trapped at the interfaces between the nanocrystals and matrices were observed.

Incoherent co-tunnelling in metallic ultrasmall-tunnel-junction systems is studied at high temperature, , in a constant-lifetime approach involving intermediate virtual states. For the double junction the resulting conductance increases linearly with the temperature. For the serial array a sharp drop off of the conductance with the number of junctions in the array is found.

Many single electron tunneling (SET) devices have been proposed to function as voltage or current dependent oscillators. Modeling the behavior of such devices in time and frequency domains is therefore needed in order to understand and predict the coherence and stability of the resulting oscillations. This paper presents a model that captures the statistics of the time domain properties together with the power spectral density of the SET signal. The technique is based on the determination of the distribution of time between events at a reference output junction. The model is then used to study the coherence of oscillations in long arrays of quantum dots. It is shown that longer arrays would generate more coherent oscillations than shorter arrays. The technique presented in this paper could be extended to simulate and study other SET configurations.

The need to organize metal nanoparticles in three, two, or one dimension(s) is linked with their properties, the use of which is only possible if they are organized. The most important properties of nonmagnetic and magnetic metal nanoparticles are therefore briefly discussed. Organization in three dimensions (3D) may happen by naturally happening crystallization processes or by linking the particles with the help of spacer molecules of various length and composition. 3D organized metal particles are quite well investigated and electron transport between the building blocks is satisfyingly understood. 2D arrangements result either by spontaneous self-assembly from solution on appropriate supports, by guided self-assembly, supporting the organization process, for instance, by means of pressure (Langmuir–Blodgett) or pre-prepared surfaces, or the most attractive kind of organization, the aimed one, since it results in artificial structures that would be necessary if nanoparticles should find application in future nanodevices. Two routes to aimed structures have become known up to now: the dip-pen nanolithography and the nanoelectrical modification of surfaces. Dip-pen nanolithography uses the transport of special molecules from a moving AFM tip to suited surfaces. Chemical modifications of as-prepared structures end up with formation of aimed patterns of metal nanoparticles. Nanoelectrical modification of CH3-terminated surfaces, also using an AFM tip, give COOH functions that can further be modified to bind metal nanoparticles. Architectures performed by one of these methods simply depend on the software the AFM is moving on the surfaces. Keywords: single electron tunnelling; magnetism; 3D; 2D; 1D organization; dip-pen nanolithography; nanoelectrical oxidation

Ligand-stabilized gold nanoparticles (AuNPs) are of high interest to research dedicated to future technologies such as nanoelectronics or biomedical applications. This research interest arises from the unique size-dependent properties such as surface plasmon resonance or Coulomb charging effects. It is shown here how the unique properties of individual AuNPs and AuNP assemblies can be used to create new functional materials for applications in a technical or biological environment. While the term technical environment focuses on the potential use of AuNPs as subunits in nanoelectronic devices, the term biological environment addresses issues of toxicity and novel concepts of controlling biomolecular reactions on the surface of AuNPs.

International audience; We are interested in the out of equilibrium phenomena observed in the electrical conductance of disordered insulators at low temperature, which may be signatures of the electron coulomb glass state. The present work is devoted to the occurrence of ageing, a benchmark phenomenon for the glassy state. It is the fact that the dynamical properties of a glass depend on its age, i.e. on the time elapsed since it was quench-cooled. We first critically analyse previous studies on disordered insulators and question their interpretation in terms of ageing. We then present new measurements on insulating granular aluminium thin films which demonstrate that the dynamics is indeed age dependent. We also show that the results of different relaxation protocols are related by a superposition principle. The implications of our findings for the mechanism of the conductance slow relaxations are then discussed.

Ultrasmall ( 5 nm in lateral diameter) double-barrier tunnel junctions have been realized using a scanning tunnelling microscope, and an optimized metal particle-oxide-metallic substrate system. Three electrical transport effects, all in good agreement with the semi-classical theory of single-electron tunnelling, have been found at room temperature: the Coulomb gap, the Coulomb staircase and zero-bias conductance oscillations as a function of tip-particle distance.

A series of sub-threshold resonances have been observed in the source-drain I ( V ) characteristics of a symmetric double harrier gated resonant tunnelling device. The structure is unaffected when the area of the device is reduced by as much as 50% and is independent of temperature between 35 mK and 10 K. The origin of this structure is neither lateral quantisation nor Coulomb blockade. The amplitude of the first peak in this structure (∼ 18 pA) implies that it is due to single electron tunnelling. We propose a model based upon tunnelling through the hound states of a single donor in the active region of the device.

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 scenarii., Comment: published in European Physical Journal B

Although I am a solid state experimentalist, I have spent most of last year dispensing with experiments and thinking exclusively about how I could create devices that could have an impact on quantum computation. I have even stopped worrying about particular devices and have started thinking about the general principles that might be useful for guiding us in thinking about which particular systems and devices could have an impact in this area.

We show that the presence of inevitable impurities in the semi-insulating GaAs domains when manufacturing a single electron transistor (SET) alters the quantisation mechanism of the single electron tunnelling through its course inside the island. Moreover, these impurities affect the amount of energy needed to change the number of electrons on the island. This decreases drastically the quality of the SET. The published experimental data (I-V characteristics) of GaAs nano-crystals has been well fitted to our model.