STM light emission from Ag/Si(111)

A light detection system combined with UHV scanning tunneling microscopy (STM) was constructed using an ellipsoidal mirror for light collection. The system was applied to the light emission from a flat (111) surface of a silver film with a tungsten tip in the STM. Improvement in the stability and quality of the emission spectra was achieved by cooling the sample to 80 K and decreasing the tunneling current from 500 to 50 nA. We also succeeded in observing a photon map of the silver surface at 80 K. The observed spectra taken under various sample bias voltages were compared with those calculated using the theory. The peaks in the spectra could be assigned as the multipole modes of the local plasmon formed between the tip and the surface. (C) 1999 Elsevier Science B.V. All rights reserved.