Molecule-Dependent Quantum Yield in Photon Emission Scanning Tunneling Microscopy of Mixed Amphiphile Monolayers on Au(111)
Contrast in photon quantum yield between photo-oxidized and reduced thiols comprising a mixed amphiphile monolayer on Au(111) was observed using a photon collecting apparatus integrated with an ultrahigh vacuum STM. The photon quantum yield of the two species differed by =30% and each was measured to be nominally independent of tunneling gap width. The spatial resolution of the photon maps was indistinguishable from that of the topographs. These results suggest that photons emitted by a scanning tunneling microscope may be useful to garner chemical information at high spatial resolution on molecularly heterogeneous surfaces.