Localized photoresponses of nanostructured metal surfaces observed by a scanning tunneling microscope

Abstract

The effect of photoirradiation of nano-gaps (tunneling junctions) between gold substrates and the probe tips of a scanning tunneling microscope (STM) was investigated for several nanostructured Au surfaces such as atomically flat Au (111), surface-roughened Au, and Ag-cluster/Au. Irradiation with 830 nm laser light resulted in time-dependent changes in the tip position and the tunneling current. The changes were mainly caused by thermal expansion of the Au substrate and the tip in the irradiated area. The expansion depended on the morphology of the Au surfaces; roughened surfaces showed larger expansion than flat surfaces. Scanning the tip during irradiation showed position-dependent responses in the current. In particular, Ag-cluster/Au showed an apparent increment in the current at the position of the deposited Ag clusters.