Browsing by Subject "Nanoelectronics--Materials."

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Open Access
Graphene based optoelectronics in the visible spectrum
(2015) Polat, Emre Ozan
Graphene, a two dimensional crystal of carbon atoms, emerges as a viable material for optoelectronics because of its electrically-tunable broadband optical properties. Optical response of graphene at visible and near infrared frequencies is defined by inter-band electronic transitions. By electrical tuning of the Fermi energy, the inter-band transitions can be blocked due to Pauli blocking. However, controlling inter-band transitions of graphene in the visible and near infrared wavelengths, has been an outstanding challenge. We developed a new device to control optical properties of graphene in the visible spectra. Our device relies on a graphene supercapacitor which includes two parallel graphene electrodes and electrolyte between them. Mutual gating between graphene electrodes enables us to fabricate optical modulators which can operate in the visible and near-infrared. Single layer graphene, however, has performance limits due to its small optical absorption defined by fundamental constants. We extend our method and we developed a new class of electrochromic devices using multilayer graphene. Fabricated devices undergo a reversible color change with the electrically controlled intercalation process. The electrical and optical characterizations of the electrochromic devices reveal the broadband optical modulation up to 55 per cent in the visible and near-infrared. Integration of semiconducting materials on unconventional substrates enables optoelectronic devices with new mechanical functionalities that cannot be achieved with wafer-based technologies. As a novel application, we demonstrate ultra thin electronic paper displays using the multilayer graphene as a reconfigurable optical medium. We anticipate that the developed devices would find wide range of applications in optoelectronics.
Open Access
Novel plasmonic devices for nano-photonics applications
(2013) Şahin, Levent
Plasmonics have attracted a great deal of interest because of their potential to design novel photonics devices which have unique optical properties. This dissertation focuses on novel plasmonic device designs for photonics applications. Electromagnetic properties of metamaterials are characterized and the resonance mechanism of Split Ring Resonator (SRR) structure is investigated. Furthermore, novel SRR-based metamaterial structures are studied. We demonstrated the significant plasmonic enhancement in the transmission characteristics through a sub-wavelength aperture by utilizing SRR resonances. Electrical tuning of plasmonic resonance with varying gate bias by using graphene is observed. Also, electrical properties of graphene is investigated. Fabrication of electrically gated graphene based plasmonic structures are realized. In addition, we utilized metamaterials to design novel photonic devices and we experimentally studied and numerically verified the novel propagation characteristics of graphene-based photonic devices and 3D nanostructures. The proposed structures are designed, simulated, fabricated and measured. The simulations and experimental results are in good agreement and shows significant enhancement of transmission characteristics of plasmonic devices. The dimensions of the structures that are designed in our work is less than 10 times smaller than the incident wavelength (r/λ~0.1) which is a desired property for enhanced light confinement of sensors. Also, the gate tuning of SRR's plasmonic resonance is the first demonstration in the contemporary literature according to our knowledge.