| Summary: | Three candidates for micro- to nano-scale light sources for application in various forms of scanning probe optical microscopy are investigated and optimised. These are sharp gold tips, nano-apertures in patterned silver films and light emitting metal-insulator-metal tunnel junctions. A safe fabrication method was developed and optimised for making sharp « 25 nm end radius), symmetric Au tips for use in light emission in ambient scanning tunnelling microscopy. The Au tips were produced using a 2-step etching process in an electrolyte comprising a 20% CaCh solution. High resolution in both topography and photon mapping . was achieved using these Au tips. Surface plasmon polaritons (SPPs), selectively excited in attenuated total reflection (ATR) with an incident annular laser beam, formed with a novel conic input optics set-up, enhances the optical transmission through a sub-wavelength aperture in a silver film. The use ofan ion beam milled, circular grating pattern on the output face ofthe silver film, concentric with the aperture, gave a further enhancement by a factor of 5 and a total enhancement by a factor up to 40 relative to the off-resonance transmission through an identical sub-wavelength aperture in a smooth metal film. Micro-scale light emitting tunnel junctions (LETJs) were fabricated capable ofwithstanding an applied bias ofup to 4V. LETJs with small dimensions (on the scale ofthe fast mode SPP propagation length) have a greater overall quantum efficiency that those of larger dimension junctions and reduce the gap in photon emission efficiency between the high (>2.5 eV) and low energy «2.5 eV) regimes. Both features are explained in terms ofthe proportion offast mode SPPs that can propagate to, and scatter from the edges ofthese otherwise smooth devices.
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