Size Dependence of the Electronic Properties of Tantalum Nanoclusters

The results of the scanning tunneling spectroscopy study of the electronic states of tantalum nanoclusters on a silicon substrate are presented. Nanoclusters are fabricated by cluster deposition from the gas phase using magnetron sputtering of a tantalum target. Clusters are formed using a Nanogen-50 cluster source (Mantis Deposition) with a quadrupole mass filter integrated into the preparation chamber of an Omicron Multiprobe MXPS VT AFM-25 ultrahigh vacuum system. It is established that the tunneling current differs significantly for spherical nanoclusters of different sizes, and the measured differential current–voltage characteristic of nanoclusters near the Fermi energy is nonmonotonic, which may indicate a change in the density of states near the Fermi energy. This change in the tunneling conductivity of nanoclusters depending on their size indicates the metal–nonmetal transition in metal nanoclusters on the semiconductor surface as the cluster size decreases.