An ultrahigh-vacuum scanning tunneling microscope with an optically transparent tip was used to excite photon emission from a clean Cu(1 0 0) surface and a sub-monolayer of Cu-tetra-[3,5-di-t- butylpheny1] porphyrin (Cu-TBPP) molecules chemisorbed on a Cu(1 00) surface. Photons generated in a nanometer- scale area just under the tip were collected within the near-field region through the apex of the optical fiber tip. Two kinds of mechanisms for the photon emission from a Cu-TBPP/Cu(1 0 0) surface are proposed. The quantum efficiency for molecular fluorescence induced by inelastic tunneling was estimated to be 3 10^-6 photons/electron.

DOI:10.1016/S0039-6028(01)01286-9