Time-Resolved Tunneling Electron-Induced Anti-Stokes Raman Spectroscopy of Interface Aggregate

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This project has aimed to improve spatial resolution of Raman and luminescence spectroscopy. A variety of samples such as carbon nanotubes, gold-metal nano triangles, molecular aggregates were adsorbed at the surfaces of graphite or indium tin oxide plates. The instruments for these measurements were designed and built up in the laboratory. Tunneling probes were made with the electro-chemical etching of silver/copper metal alloy wires or chemical coating of silver metal on electro-chemically sharpened tungsten wires. We have found that the spatial resolution of Raman spectroscopy was improved to be in the range of several tens of nanometer when nanotubes were measured ; however, the topographical images did not always correspond with the spectral images. This deviation is considered to be due to differences in the spaces where the plasmonic enhancement takes place and the tunneling current flows. Photoluminescence of cadmium serenade quantum dots on indium tin oxide plates showed significant dependence on the distance between the quantum dots and tunneling probes with a nanometer precision. Gold nano triangles adsorbed on indium tin oxide surfaces were found to give good atomic-flat surfaces for scanning tunneling microscopy as well as to give semi-transparent substrates for inverse-type optical microscopy. Moreover, we found that some parts of gold nano triangles emitted luminescence only by approaching tunneling probes. These results are expected to contribute the development of high spatial resolution spectroscopy for the nano world.