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We fabricated tunnel junctions containing clusters embedded in a thin insulating layer. Low-temperature dc transport measurements reveal typical Coulomb blockade features. We measured the differential capacitance at different dc voltages and frequencies of these samples in the Coulomb blockade regime. The differential capacitance is constant at low dc bias and increases by 35% above a threshold voltage. This behavior can be well understood using a simple model which takes into account the Coulomb blockade effect. Such measurements could be used as a probe of Coulomb blockade properties of clusters assemblies. This effect is also promising for the fabrication of capacitors whose capacitance can be changed by varying the applied voltage. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We investigate the magnetotransport characteristics of nanospintronics single-electron devices. The devices consist of single nonmagnetic nano-objects (nanometer-size nanoparticles of Al or Cu) connected to Co ferromagnetic leads. The comparison with simulations allows us attribute the observed magnetoresistance to either spin accumulation or anisotropic magneto-Coulomb effect (AMC), two effects with very different origins. The fact that the two effects are observed in similar samples demonstrates that a careful analysis of Coulomb blockade and magnetoresistance behaviors is necessary in order to discriminate them in magnetic single-electron devices. As a tool for further studies, we propose a simple way to determine if spin transport or the AMC effect dominates from the Coulomb blockade I-V curves of the spintronics device. [ABSTRACT FROM AUTHOR]

The growth of a nanocluster assembly on a processed AlOx and its electronic transport behavior are investigated. An Ar+ plasma was used in order to create defects of high trapping energy on an AlOx layer. This process promotes a shift of the cluster distribution towards smaller sizes and allows to sharpen it. In a second part, the authors show that the application of this techniqueto clusters inserted in a tunnel junction can lead to a dramatic increase in the temperature range over which Coulomb blockade can be observed. [ABSTRACT FROM AUTHOR]