Browsing by Author "Uran, Can"

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Open Access
Arrays of suspended plasmonic nanodiscs
(IEEE, 2013) Uran, Can; Demir, Hilmi Volkan
We demonstrate lateral arrays of suspended metal nanodiscs, erected in parallel, partially encased in a dielectric-wrap using in-template synthesis with their polarization-dependent properties controlled as a function of disc-gap/-width tailoring their scattering/absorption spectra. © 2013 IEEE.
Open Access
Fabrication of an on-chip nanowire device with controllable nanogap for manipulation, capturing, and electrical characterization of nanoparticles
(2008) Uran, Can
One of the major challenges in nanofabrication commonly arises from the necessity to integrate nanostructures (e.g., nanoparticles) on the same chip with microcomponents (e.g., microelectrodes) that are orders-of-magnitude larger in size. For example, in order to make electrical contacts to colloidally synthesized nanoparticles (typically 1-100 nm in size) by integrating them with microelectrodes (typically in the few micrometers range on the critical side), a large size mismatch that easily ranges from 1:10 to 1:10,000 is required to be handled delicately for successful nano-to-micro integration. This necessitates the ability to manipulate and integrate nanoparticles with a sufficient level of precision on the microchip. In this thesis, to provide a convenient solution to this challenging problem, we proposed and demonstrated for the first time an onchip nanowire device that features a controllable nanogap in its architecture for capturing and electrical characterization of nanoparticles in the gap, all fully integrated on the same microchip. Our innovative approach relies on the use of dielectrophoretic electric-field assisted self-assembly of our segmented nanowires to construct a nanoscale device platform. For this purpose, we synthesized gold-silver-gold segmented nanowires and dielectrophoretically aligned them across our microfabricated array of electrodes. Subsequently, we selectively removed the middle silver segment to open a gap in the nanometer size between the self-aligned gold end segments. Using dielectrophoretic assembly once more, we captured nanoparticles in these nanogaps for further electrical characterization. One of the key benefits in our approach was that the aligned nanowires automatically provided electrical contacts to the captured nanoparticles to allow for electrical probing at the nanoscale. Our innovative approach enabled convenient full integration from nanoparticles to nanowires to microelectrodes to macroprobes on a single chip, spanning a size range of more than six orders of magnitude.
Open Access
On-chip integrated nanowire devices with controllable nanogap for manipulation, capturing, and electrical characterization of nanoparticles
(IEEE, 2009) Uran, Can; Ünal, Emre; Kizil, R.; Demir, Hilmi Volkan
Dielectrophoresis (DEP) allows for electric field assisted assembly in spatially non-uniform field distribution, where the induced moment is translated into a net force on polarized particles towards the high field gradient. For example, for a spherical particle of radius r with a permittivity constant ofεp in a host medium with the permittivity ofε m, the dielectrophoretic force is given by (1): where r is the particle radius, ω is the angular frequency and Erms is the root mean square electric field. K is the Clausius-Mossotti function, which depends on the complex permittivity of the spherical particle and the medium [1].IEEE.
Open Access
Solution-processed nanostructures and devices for highly polarized light generation, scattering and sending
(2014) Uran, Can
Recent advancements in photonics have facilitated robust and reliable light sources, displays and photosensors with relatively long lifetimes and high energy efficiency in their classes. However, developing intrinsically polarization selective photonic devices still remains a challenge, although polarization sensitivity is essential to various advanced functions and/or improved performance. One of the main difficulties in making such devices emerges from the compromise on the efficiency while striving to reach high polarization contrast levels. For instance, commercially available birefringent structures including those integrating liquid crystals suffer from major transmission losses. On the other hand, solutionprocessed, high aspect-ratio nanostructures may offer power efficient platforms with high polarization contrasts via selection of the polarization in a preferred direction during emission, absorption and/or scattering process(es) while suppressing efficiency of the relevant ones in the other polarization. In this thesis, we present solution-processed metal and semiconductor nanostructures and optoelectronic devices made from them for highly polarized light generation and enhanced photosensing. Here we developed and demonstrated in-template fabricated suspended arrays of plasmonic thin nanodiscs with tunable disc-heights and gap-widths tailoring absorption and scattering properties for applications ranging from polarized light scattering to photodetection. Also, we proposed and showed highly polarized light emission in coupled thin films of magnetically aligned multisegmented nanowires and colloidal nanocrystals for polarized color enrichment in displays. Here well-controlled in-template synthesis of these nanowires together with their alignment under magnetic field allows for highly parallel orientation of the nanowires in massive numbers over large-area thin films. Integrating with color-enriching nanocrystals, this enabled a record high polarization contrast over 15:1 for the isotropic nanocrystals in the visible range. We believe that such hybrid assemblies of solution-processed nanostructures integrated into optoelectronic devices hold great promise for advanced functions in photonics.