Phd Degree / Doktora
Permanent URI for this collectionhttps://hdl.handle.net/11147/2869
Browse
3 results
Search Results
Doctoral Thesis Markov Olmayan Ortamlar ile Etkileşimdeki Süperiletken Transmon Kübitlerin Kesirli Dinamiği(01. Izmir Institute of Technology, 2025) Savacı, Ferit Acar; Erdoğan, Ruha Uğraş; Savacı, Ferit AcarBu tezde, literatürde ilk defa olmak üzere, Mittag-Leffler (ML) tipi ilintilerin Markov bir çevre ile etkileşimde olan transmon kübitlerin eşfazlılık sürelerinin iyileştirilmesine olan etkisini irdeledik. Tez kapsamında gerçekleştirdiğimiz ikinci çalışmada, literatürde ilk defa, amorf bir çevre içindeki kusur ile etkileşimde olan transmon kübitin zaman dinamiğini analiz ettik. Markov karakteristiğine sahip gürültü eksenine dik uygulanan ML ilintili gürültüye ait karakteristik üstelin (KÜ), eşfazlılık süresine ve kubit durum dağılımına etkisini analiz ettik. Bu kapsamda yayıngan ve rastsal telegraf gürültüsünün kesirli genelleştirilmesinden inşaa ettiğimiz iki tip ML ilintili gürültü kullandık. Eşfazlılık süresinin KÜ ile ifade edilen hafızaya bağlı olarak arttığını gözlemledik. Transmon kübit ve üzerinde üretim aşamasında oluşan amorf kaplamadaki tek bir kusur arasında Gaussian olmayan karakteristiğe sahip enerji yayılımına sebep olabilecek, aynı zamanda etkileşimdeki sistem dinamiğinde uzun süreli hafızaya sebep olabilecek ağır kuyruklu Lévy tipi enerji salınımlarını irdeledik. Çevrenin güç tayfı yoğunluğunun zaman bağımlı olma durumunu zamana bağlı kesirli üstel ile betimledik. Bu ifadeye bağlı olarak, transmon kübitin zaman dinamiğini değişken mertebeli kesirli ana denklem ile ifade ettik; zamana bağlı KÜ ile betimlenen ortamın, kübit eşfazlılık süresine etkisinin, açık kuantum sistemlerinde ilk olmak üzere, bilgisayar benzetimlerini gerçekleştirdik.Doctoral Thesis Optimization of Zinc Oxide Based Metal - Semiconductor Junction Interface Properties and Applications for Optoelectronic Devices(01. Izmir Institute of Technology, 2024) Güzelaydın, Abdurrahman Halis; Tarhan, EnverThis thesis manifests an experimental investigation on the optoelectronic characteristics of wide band gap thin film zinc oxide semiconductor – metal junction and performance enhancement of ultraviolet photo detectors fabricated utilizing this metal-semiconductor interface. Pristine zinc oxide, aluminum doped zinc oxide and amorphous In-Ga-Zn-O thin film samples with thicknesses varying between 50-250 nm were fabricated from 2' ceramic targets via magnetron sputtering method. Surface properties and thus the zinc oxide – metal junction interface was optimized by altering sputtering parameters. Sputtering gas pressure, power and temperature was varied between 1.5 – 5 mTorr, 50 – 120 W and 25 – 500 °C, respectively. To determine the effects of energetic ion bombardment on the films' surface properties, biases ranging from 5 to 15 W were applied to the substrates during depositions. A 5 nm thick silicon dioxide passivation layer was deposited on zinc oxide thin films to suppress persistent photoconductivity effect. Furthermore, a thermal treatment under ultraviolet irradiation and was applied specifically to amorphous In-Ga-Zn-O thin films after device fabrication to improve their ultraviolet sensing capabilities. Optoelectronic spectral responses of devices were assessed experimentally by using transient photocurrent spectroscopy method. An ultraviolet light source with a 275 nm peak wavelength at 500 µW power was used as illumination source. All devices exhibited photoconductor behavior with ohmic metal-semiconductor junctions under 5 V bias. Amorphous In-Ga-Zn-O Sample 10 attained a dark current of 140 nA and reached a photocurrent level of 3.8 µA with a photo-to-dark current ratio of 27, yielding a spectral response of 1830 A/W. The calculated external quantum efficiency for this device was 825000%.Doctoral Thesis Synthesis, Properties and Applications of Tungsten Oxide Nanostructures(01. Izmir Institute of Technology, 2023) Kahraman, Zeynep; Balcı, Sinan; Genç, AzizIn this study, tungsten oxide nanostructures, which are n-type semicon ductors with a band gap between 2.6-2.8, have been studied extensively. The hydrothermal method was used as the synthesis technique and the phases and morphologies were optimized in a stable and controllable manner. Firstly, sto ichiometric tungsten oxide nanowires with certain ratios were synthesized, and then cobalt doping was made using this synthesis technique. Subsequently, sub-stoichiometric tungsten oxide nanowires, which have oxygen gaps and can show plasmonic properties due to the increased carrier density, were synthe sized, and tungsten oxides with a flower-like hierarchical structure with oxygen gaps were synthesized and grouped according to possible application areas. Accordingly, how oxygen vacancies and hierarchical structures affect pho tocatalysis applications have been examined and it has been seen that ub stoichiometric tungsten oxide works faster until it reaches a certain saturation than stoichiometric tungsten oxide. According to this study, how the system can be manipulated by adding low pH to the system and hydrogen peroxide as an electron acceptor, respectively. It has been observed that it can be done. Hierarchical tunsten oxide has been found to be an ideal catalyst that can work quickly in photocatalysis studies due to its hierarchical structure, which has oxygen vacancies and can absorb light well. Additionally, tungsten oxide attracts attention as a material used in su percapacitor applications. Supercapacitors are long-lasting and fast-reacting electrochemical devices that can provide high power in energy storage and dis charge processes. The use of tungsten oxide in supercapacitor applications can be summarized as follows: when nanoparticles with large surface area are used as electrode material, they increase the interaction with the electrochemical surface and can increase the energy storage capacity. It shows high electro chemical activity as an electrode material. This feature contributes to the high performance of the supercapacitor. Tungsten oxide has a structure suitable for electron and ion conduction. This allows the supercapacitor to have fast charge/discharge capabilities and low internal resistance. Tungsten oxide can show stable performance during electrochemical cycles. This feature ensures the long life of the supercapacitor. In supercapacitor applications, in addition to these features, the electrical conductivity of the material can be increased by increasing the number of electrons carried in the material due to its oxygen gap. Accordingly, we investigated the comparative electrochemical properties and cycling stability of stoichiometric and sub-stoichiometric nanowires. Thanks to its electrochromic properties, the latest application has observed electrochromic changes of oxygen vacancies and cobalt doping