PHOTON-EMISSION FROM SI(111)-(7X7) INDUCED BY SCANNING-TUNNELING-MICROSCOPY - ATOMIC-SCALE AND MATERIAL CONTRAST

Photon emission from the scanning tunneling microscope provides a sign al which is dependent on the local chemical environment beneath the ti p, but the details of material contrast have not been previously studi ed. Here we describe photon maps with material contrast, where the spa tial resolution of this chemical dependent signal is a few nanometers. The resolution is governed by the size of the localized plasmon benea th the tip, which is responsible for the photon emission, and we sugge st how the resolution can be made subnanometer.