Browsing by Subject "Fabrication and characterizations"

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Open Access
Fabrication and characterization of SmCo5/Nb ferromagnetic/superconducting hybrid thin films grown by RF magnetron sputtering technique
(Elsevier, 2017) Ongun, E.; Kuru, M.; Serhatlıoğlu, M.; Hançer, M.; Ozmetin, A. E.
Ferromagnet/Superconductor (F/S) bilayer hybrids show exclusive states due to the mutual interaction between the superconductor and the underlying ferromagnetic substructures in micron scale. In this work, we aimed to observe the effects of the interaction between superconductivity and magnetism, especially the phenomenon involving the orientation and the size of magnetic stripes has been investigated in a coupled ferromagnetic/superconducting thin-film structure. In the proposed F/S hybrid system by this work, superconducting niobium thin-films were combined with underlying segments of ferromagnetic SmCo5 substructures. 300 nm thick magnetic films fabricated by RF magnetron sputtering techniques were topographically grown in patterns with stripes oriented either transverse to or along the direction of current flow. The elemental and microstructural analyses were conducted by EDX, SEM and GIXRD characterization tools. Low-temperature DC transport measurements were conducted by means of four point probe method in a 9T closed-cycle cryogenic refrigeration system. Transport superconducting properties, transition temperature TC(H) and second critical field HC2(T) were measured in a range of applied magnetic field between H = 0–9 kOe for the hybrid system. The results revealed that the artificial periodic modulation of applied field through preferentially-oriented magnetic stripes could introduce normal and superconducting channels or barriers for the current flow.
Open Access
Metal-semiconductor-metal UV photodetector based on Ga doped ZnO/graphene interface
(Pergamon Press, 2015) Kumar, M.; Noh, Y.; Polat, K.; Okyay, Ali Kemal; Lee, D.
Fabrication and characterization of metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) based on Ga doped ZnO (ZnO:Ga)/graphene is presented in this work. A low dark current of 8.68 nA was demonstrated at a bias of 1 V and a large photo to dark contrast ratio of more than four orders of magnitude was observed. MSM PD exhibited a room temperature responsivity of 48.37 A/W at wavelength of 350 nm and UV-to-visible rejection ratio of about three orders of magnitude. A large photo-to-dark contrast and UV-to-visible rejection ratio suggests the enhancement in the PD performance which is attributed to the existence of a surface plasmon effect at the interface of the ZnO:Ga and underlying graphene layer.
Open Access
Tunable ring-coupled Mach-Zehnder interferometer based on lithium niobate
(Taylor and Francis, 2014) Solmaz, M. E.
The fabrication and characterization are reported of a Fano resonance-based electro-optically tunable ring resonator-coupled Mach-Zehnder interferometer device based on a chalcogenide-lithium niobate hybrid waveguide system. The experiments reveal inherent asymmetric lineshapes that can be flipped to a near symmetrical resonance by applying a dc voltage of ~10 V across the electrode at the MZI non-resonator arm. Further increase in voltage yields the reverse of initial asymmetry. The optical filter-based transfer-matrix model easily explains the experimental data and indicates ways to further enhance the usability of such architecture. © 2014 Taylor and Francis.