Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Conference Object Graphene-Based Integrated Electronic, Photonic and Spintronic Circuit(SPIE, 2013) Potasz, P.; Güçlü, Alev Devrim; Özfidan, Işıl; Korkusinski, Marek; Hawrylak, PawelTo create carbon-based nanoscale integrated electronic, photonic, and spintronic circuit one must demonstrate the three functionalities in a single material, graphene quantum dots (GQDs), by engineering lateral size, shape, edges, number of layers and carrier density. We show theoretically that spatial confinement in GQDs opens an energy gap tunable from UV to THz, making GQDs equivalent to semiconductor nanoparticles. When connected to leads, GQDs act as single-electron transistors. The energy gap and absorption spectrum can be tuned from UV to THz by size and edge engineering and by external electric and magnetic fields. The sublattice engineering in, e.g., triangular graphene quantum dots (TGQDs) with zigzag edges generates a finite magnetic moment. The magnetic moment can be controlled by charging, electrical field, and photons. Addition of a single electron to the charge-neutral system destroys the ferromagnetic order, which can be restored by absorption of a photon. This allows for an efficient spin-photon conversion. These results show that graphene quantum dots have potential to fulfill the three functionalities: electronic, photonic, and spintronic, realized with different materials in current integrated circuits, as well as offer new functionalities unique to graphene.Article Citation - WoS: 20Citation - Scopus: 23Effect of Humidity on Electrical Conductivity of Zinc Stearate Nanofilms(Elsevier Ltd., 2007) Öztürk, Serdar; Balköse, Devrim; Okur, Salih; Umemura, JunzoIn this work, stearic acid (StAc) and zinc stearate (ZnSt2) nanofilms were deposited on glass and silver substrates using Langmuir-Blodgett (LB) film technique and their structural and electrical properties were investigated. X-ray diffraction and IR techniques revealed that more crystalline and better films were obtained from ZnSt2 compare to StAc. Electrical conductivity of ZnSt2 LB films with 13 layers having 28 nm thickness were measured in the range of humidity of 20-60% and it is seen that the conductivity was very sensitive to relative humidity (RH) above 40% at 25 °C and showed no hysteresis during adsorption and desorption of water vapor. Water vapor adsorption isotherm of ZnSt2 powders was determined and conductivity increase with humidity was attributed to water vapor adsorption. Constant electrical conductivity of the ZnSt2 films at low relative humidities and at low voltage values is an advantageous property which allows using them as organic nanofilms with insulating properties.Article Citation - WoS: 74Citation - Scopus: 77Full Bulk Spin Polarization and Intrinsic Tunnel Barriers at the Surface of Layered Manganites(Nature Publishing Group, 2005) Freeland, John W.; Gray, Kenneth E.; Özyüzer, Lütfi; Berghuis, Peter; Badica, E.; Kavich, Jerald J.; Zheng, Hong; Mitchell, John F.The affect of full bulk spin polarization and intrinsic tunnel barriers on the surface of layered manganites were studied using a combination of surface-sensitive x-ray and tunnelling process. The surface bilayer of air-cleaved layered manganites forms an antiferromagnetic insulating nanoskin composed of a single bilayer unit. It was shown that for the quasi-two-dimensional bilayer manganites the outermost Mn-O bilayer is affected while the next bilayer displays the full spin polarization of the bulk. The results show that the outermost bilayer act as an intrinsic barrier between the fully spin-polarized bilayer beneath and a subsequently deposited ferromagnetic counterelectrode.