Doctor of Philosophy (Ph.D.)
Rosa A. Lukaszew
Photocathodes play an important role in present large accelerator facilities by providing polarized or un-polarized electron beams. Current state-of-art high polarization photocathodes consist of strained super-lattice GaAs based photocathodes, e.g. GaAs/GaAsP has a quantum efficiency ~1% and polarization ~90% at near-infrared wavelength for the incident light. Despite the advantages offered by metallic photocathodes regarding longer life time, fast response time and low requirements of ultra-high vacuum environment, they have not been put to use due to their low quantum efficiency, even though one can envision several approaches to achieve spin-polarization from them. A possible solution is to apply the Fano resonance, that involves coupling the surface plasmon resonance and the 1st diffraction order of incident light on a corrugated silver surface. This thesis demonstrates that this approach yields an enhancement of the QE performance of a cesiated silver grating cathode for light incident at the resonance angle, compared to that of a cesiated flat silver cathode measured in the same system. By altering the grating profile through oblique angle deposition (OAD) of a silver thin film onto a grating surface using magnetron sputtering deposition, one can further enhance the Fano resonance and consequently improve the electric field intensity near the silver cathode surface. QE measurements confirm an enhancement of QE (26%) on the cesiated OAD sample compared to a cesiated one obtained under normal deposition(ND) for light incident at resonance, respectively, showcasing a possible road for metallic photocathodes for this application.
© The Author
Li, Zhaozhu, "Plasmonic Approaches and Photoemission: Ag-Based Photocathodes" (2017). Dissertations, Theses, and Masters Projects. Paper 1516639865.
Available for download on Saturday, October 06, 2018