Enhanced photon emission from the STM: a general property of metal surfaces

Light emission observed from noble-metal surfaces in an STM has been interpreted as arising from inelastic tunneling excitation of radiative tip-induced plasmon modes. We discuss recent extensions of this work to clean and oxygen-covered transition metal surfaces. Photon intensities observed in the tunnel mode permit mapping and spectroscopic investigation of sub-nanometer areas of the surfaces of Cu, Fe, and Ti. Our results corroborate the theory developed for noble metals. Contrasts in photon maps on an atomic scale caused by adsorbates are discussed. © 1992.