Patterning of Narrow Au Nanocluster Lines Using V2O5 Nanowire Masks and Ion-Beam Milling

摘要

In recent years there has been considerable interest in metallic and semiconducting nanoclusters for a variety of reasons, not least of which is their potential for electronics and sensors. Although there are worthwhile applications of these clusters in devices at the micron scale, e.g., in chemical vapor sensing, the most intriguing possibilities arise when the numbers of clusters are reduced to a relative few and the inherent scalability associated with their nanoscale dimensions is fully exploited. One set of such possibilities involves metallic nanoclusters whose ultra-small sizes (< 2- 3nm in diameter) imply large charging energies and hence strong Coulomb blockade even at room temperature. For the blockade phenomenon to be manifested in an electrical signal one needs to minimize statistical averaging effects by having only small numbers of nanoclusters participate in the transport processes. The extreme example is the limit of a single cluster that has been studied extensively using scanning tunneling microscopy (STM). A more practical configuration involves 'small' numbers of clusters arrayed between two nanoscale electrodes defined on the surface of an insulator with possibly a third terminal situated on the surface or on the backside. This arrangement has been explored in a number of experiments and a variety of Coulomb blockade signatures have been observed. In the simplest case, the restriction on the numbers of clusters comes about merely by having small enough electrodes and relying on the Coulomb threshold to suppress fringing currents. More sophisticated efforts position the clusters between the electrodes using e-beam lithography, atomic force microscope (AFM) manipulation or electrostatic trapping. Although these latter methods work, they have drawbacks including that they have not yet been successful with ultra-small clusters.