A STUDY OF METAL-FILMS USING A SPECTRALLY RESOLVED PHOTON MAP OBTAINED BY SPECTRUM MAPPING MEASUREMENTS OF STM-INDUCED LIGHT

We have carried out spectral mapping measurements of tunneling-induced luminescence in scanning tunneling microscopy (STM) of nanoscale gold metal particles on a graphite surface. The luminescence spectra are r ecorded at the same time as STM topography images by using an intensif ied charge coupled device (CCD) detector and a spectrograph. Based on the measurements, spectrally resolved photon-intensity images are obta ined for various spectral bands. Those photon-intensity images are com pared with the topography image. We have observed two types of spectra lly dependent photon images. One is associated with a shorter-waveleng th (similar to 650 nm) mode and the other a longer-wavelength (similar to 700 nm) mode. The photon map of shorter wavelength (similar to 650 nm) is correlated with grain morphology. The longer-wavelength mode r eveals a high emission intensity for some grains. The result is discus sed in relation to the microstructure geometry.