Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7755

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2008 - 200912010 - 20185

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Physics

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Now showing 1 - 6 of 6
  • Master Thesis
    Quantum Dynamics of Noise Assisted Excitation Transport
    (Izmir Institute of Technology, 2018) Özkan, Hazan; Çakır, Özgür; Çakır, Özgür; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this thesis, different types of systems are studied to investigate the effects of the environmental factors on diffusion and transfer time. Each system consists of different energy levels and excitation transfers between them. The mismatch between the energy levels leads to the Anderson localization. Localization has a negative effect on transport. It is shown that Anderson localization is suppressed due to interaction with the environment. To describe the dynamical evolution of the open quantum system Lindblad master equation is used. The transition times of the system from the pure state to the completely mixed state are examined with the help of the density matrix. In consequence of our study, because of the interaction between the system and environment the change in the wavefunction, the loss in the interference terms and an irreversible information flow in the total system are observed. Destructive effects of the environmental noise on localization are observed for different scenarios and diffusion enhanced. However, when the interaction with the environment becomes larger than a critical value, the system exhibits Zeno effect. In the Zeno regime, the time evolution of the quantum state of the system as well as the diffusion is suppressed.
  • Master Thesis
    Temperature Dependence of Resistivity and Hall Coefficient in Cu2znsns4 Absorbers for Thin Film Solar Cells
    (Izmir Institute of Technology, 2017) Akça, Fatime Gülşah; Aygün, Gülnur; Özyüzer, Lütfi; Aygün Özyüzer, Gülnur; Özyüzer, Lütfi; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    energy is the most powerful clean energy source to act on the current energy needing all over the world. The utilization of green energy systems should be promoted since these energy systems benefit consumers, industry and the environment effectively for the developing countries. This advancement can be solely achieved if renewable energy sources become more accessible. It means that not only cheaper but also handy clean energy systems are needed. In spite of relatively high efficiency obtained by using c-Si, Si solar modules require high budget for manufacturing. The high production cost of c-Si, PV industry is lead to search for cheaper candidate materials like Cu2ZnSnS4 (CZTS) as absorber layer in solar cells. The aim of the thesis is to investigate electrical properties of CZTS p-type intrinsic semiconductor compound on soda lime glass substrates, including the temperature dependent electrical conductivity, carrier concentrations and mobility extracted from Hall Effect measurements. Firstly, the metal precursor films were fabricated in multi-target sputtering system, then they were sulfurized inside the tubular furnace in order to obtain the CZTS compound. X-ray diffraction and Raman spectroscopy measurements revealed the formation of kesterite structure. A good crystallinity and grain compactness of the films were determined by scanning electron microscopy (SEM). Electrical properties were measured by van der Pauw techniques. Hall effect measurements showed the p-type semiconductor behavior for all samples at room temperature. Also, optical properties including absorption coefficient, spectral transmission, and optical band gap were determined to characterize CZTS thin films.
  • Master Thesis
    Quantum Control and Generation of Quantum Entanglement
    (Izmir Institute of Technology, 2014) Altuğ, Sevil; Çakir, Özgür; 01. Izmir Institute of Technology
    In this thesis, the generation of entanglement is studied in a controlled environment. The model system of interest includes a cavity field interacting with a pair of atoms. The cavity field is heavily damped and it is pumped in order to maintain a steady state field population. Thus, we can eliminate the cavity field adiabatically and obtain the master equation describing only the qubits evolution in time. At first, this system is analyzed in the steady state, without making any measurement on the photons leaking through the cavity walls. In this way, the ideal physical parameter set for maximum entanglement in this model is investigated. In the second step, we assume a direct measurement on the leaking cavity photons, and observe the evolution of entanglement in a quantum trajectories approach. We simulate quantum trajectories approach by applying Monte Carlo method. The amount of entanglement is obtained as a function of time and number of photon detections.
  • Master Thesis
    Fabrication and Characterizarion of Superconductor Ybco Josephson Junctions
    (Izmir Institute of Technology, 2008) Algül, Berrin Pınar; Abukay, Doğan; Abukay, Doğan; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    A well-controlled, high-yield Josephson junction production process forms the basis of superconducting electronic device and circuit technology. In order to use the Josephson junctions effectively and fabricate them reproducibly, their structural and electrical characterization should be performed.This study concentrates on the fabrication and characterization of high temperature bicrystal grain boundary Josephson junctions fabricated onto 24-dand 30-degree SrTiO3 bicrystal substrates using high quality YBa2Cu3O7-. (YBCO) thin-films.200 nm thick YBCO thin films were deposited using a dc Inverted Cylindrical Magnetron Sputtering technique by investigating the thin film deposition conditions in order to obtain device quality films. The superconducting properties of the thin films were determined by electrical characterizations, consisting of resistance versus temperature and magnetic susceptibility versus temperature measurements. Structural properties were analyzed by Atomic Force Microscope, Scanning Electron Microscope and X-Ray Diffraction.Prepared thin film samples were patterned as bicrystal grain boundary Josephson junctions by standard photolithography and chemical etching processes. The current-voltage characteristics of the Josephson junctions were performed at 77 K under zero and non-zero applied field in magnetically shielded environment. The critical current values (Ic), normal resistance (Rn) and IcRn product of the output signals were determined, and the values were discussed as function of the film growth conditions. The optimization of the Josephson junctions was performed in order to improve both the signal performance and the stability of our devices against thermal cycling.
  • Master Thesis
    Co Gas Sensor Applications of Fe Doped Calix[4] Arene Molecules
    (Izmir Institute of Technology, 2013) Özbek, Cebrail; Aygün, Gülnur; Aygün Özyüzer, Gülnur; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Invisible and odourless carbon monoxide (CO) is one of the most toxic gas for respiratory systems. Therefore, the concentration level of carbon monoxide in the environment is extremely vital. In this thesis study, Calixarene molecules have been synthesized and the carbon monoxide selectivity and sensitivity of bare and iron doped calixarene molecules were measured by quartz crystal microbalance QCM technique and interdigitated electrodes with 3 ï ­m spacing. Calixarenes are promising compounds for sensing studies due to the well-designed cyclic structure, easily derivatization at both p- position of phenolic ring (upper rim) and phenolic-O (lower rim) as well as having diversely cavities which are a straightforward platform to form complex with molecules and ions. Quartz Crystal Microbalance is a powerful technique for nano scale determining the sorption properties of materials. According to Sauerbrey relation, the mass change on quartz crystal electrode cause a certain shift in the resonant frequency of vibrating crystal oscillator. This shift can be monitored using QCM method. In this study, a computer controlled QCM measurement system was developed for toxic gas detection. Iron doped calixarene based sensors were fabricated using drop-casting method on an AT-cut QCM gold electrode and interdigitated gold electrodes. The sensitivity and reproducible detection performances of prepared calixarene-iron doped calixarene thin films were measured under exposure of varying carbon monoxide for nitrogen and dry air used as desorption gas, respectively. The analysis of carbon monoxide sensitivity of iron doped calixarene is a new study for literature. This thesis study will guide future studies on this topic.
  • Master Thesis
    Growth and Characterization of Aluminum Doped Transparent and Conductive Zinc Oxidethin Flims
    (Izmir Institute of Technology, 2010) Ataç, Derya; Selamet, Yusuf; Selamet, Yusuf; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    This thesis focuses on fabrication, characterization and understanding physical properties of transparent and conductive Al doped zinc oxide (ZnO) thin films. Films were deposited by magnetron sputtering technique, using separate ZnO and Al targets. SiO2 and glass (microscope slides) were used as substrates. Growths were performed at room temperature in Ar environment at a constant pressure of 3 mTorr. Films were characterized by atomic force microscope, x-ray diffractometer, scanning electron microscope, UV-vis spectroscophotometer and four point probe electrical measurements. Using transmission data, band gaps of the films and using four point probe measurements, resistivities of films were calculated. Firstly properties of pure ZnO films were studied. They were found to be highly transparent; however their resistivity was very high that we could not measure with our instrument. Therefore, ZnO films were uniformly doped with Al. It was seen that decreasing Al content was improving electrical and optical properties. Al concentration of the films was decreased firstly by decreasing deposition power of Al. After that, content was further decreased by depositing stacks of doped and undoped layers (modulation doping). Following that, modulation doped films were deposited with applying RF bias power to substrates. All films were annealed at 300oC for 1 hour in vacuum. The lowest resistivity obtained in this study was 1.68x10-3 .cm. Transmittance and band gap of the corresponding film were 80% and 4.1 eV respectively. The film was fabricated by modulation doping accompanied with substrate bias of 10 W, followed by annealing at 300oC in vacuum.