Nanoscale metallic clusters have potential applications in nanoelectronic circuits, nanoplasmonic devices, catalysis, and alternative energy applications. In this study, the electronic properties of gallium nanoclusters on silicon surfaces were probed at the atomic scale using ultra-high vacuum (UHV) scanning tunneling microscopy (STM). These measurements yielded clear evidence for novel electronic interactions between the nanoclusters and the substrate, which can potentially be exploited in next generation silicon-based integrated circuit technology.
Self-assembled metallic nanoclusters are of great interest because they possess size-dependent properties that make them attractive for a variety of potential applications ranging from optoelectronics to nanocatalysis. Recently, metals that form well-ordered nanoclusters templated on the Si(111)-7x7 surface have been reported. The Si(111)-7x7 surface has a rich electronic structure and has thus attracted interest for nanoelectronics, molecular electronics, and chemical sensing. In this work, we performed ultra-high vacuum (UHV) scanning tunneling microscopy and spectroscopy (STM and STS) characterization of the electronic properties of a self-assembled array of uniform Ga nanoclusters templated on the Si(111)-7x7 surface. By simultaneously mapping the topography and local density of states (LDOS) of this nanocluster array with atomic resolution, we found that there is charge redistribution across the surface that forms a two-dimensional network of increased differential tunneling conductance that connects the clusters. The spatial maps of the LDOS also indicate a close relationship between the metal clusters and Si(111)-7x7 substrate. Atomic scale spatial resolution mapping of the delocalized electronic properties of a self-assembled metal nanocluster array on the Si(111)-7x7 surface has not been previously reported. Our experimental finding of charge rearrangement for the Ga nanocluster array agrees with computational predictions of a two-dimensional electron gas (2DEG) for metal nanoclusters on this surface.
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