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Title: Microscale and nanoscale plasmonic light sources
Author: Feng, Lei
ISNI:       0000 0001 3459 2970
Awarding Body: Queen's University of Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available