Ankara : The Materials Science and Nanotechnology Program of the Graduate School of Engineering and Science of Bilkent University, 2014.Thesis (Master's) -- Bilkent University, 2014.Includes bibliographical references leaves 54-57.In this study, we design and produce grating coupled surface plasmon surfaces
which are switched by electrochemistry. Grating structures are fabricated using
digital versatile discs (DVDs) which are commercially available. According to
atomic force microscopy (AFM) results, we categorize the different grating
structures in two groups, namely shallow and deep gratings. Plasmonic properties of
the surfaces are investigated using numerical simulations. Gold and silver are used
as plasmon supporting metallic layers on gratings. Refractive index sensitivity of the
plasmon resonances are studied using deionized water, air and glycerol solutions as
the dielectric media and results are compared with simulations. Experimental results
are coherent with the simulations in terms of reflection spectra.
Electrochemical switching of plasmonic properties may have applications in
tunable and switchable filters, as well as enhanced colorimetric sensing. We deposit
ultrathin films of copper on plasmonic surfaces and investigate reversible changes in
the plasmonic properties. Copper sulfate is selected as the electrolyte. Cyclic
voltammetry is performed on plasmonic surfaces while monitoring optical
reflectance. Copper is observed to deposit in the form of nanoislands on silver and
gold films rather than uniform thin films. The effect of copper deposition on the
plasmonic properties of the grating structure is simulated by Lumerical software and is seen to be two fold. For small effective thickness of copper nanoislands, the
plasmon resonance condition shifts, whereas for thicker copper deposition
plasmonic resonances are eliminated.
Finally, copper's oxidation and reduction reactions are controlled by changing
applied voltage thus shifting the resonance wavelength. Resonances are switched
reversibly multiple times not only for different molarities but also for different
grating sructures and plasmon supporting metallic layers . In summary, we
demonstrate that plasmonic properties of nanostructured metallic surfaces can be
controlled by electrochemistry. Switchable resonance surfaces can be used as
dynamic filters or may enhanced contrast in plasmon resonance imaging
applications.Karayalçın, Nihat SerkanM.S
