Capacitance variation of an assembly of clusters in the Coulomb blockade regime

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.