GCRIS

Now showing 1 - 2 of 2

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, Enver
This 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%.
Single-Photon Generation From Defects and Manipulation With Nanostructures
(Izmir Institute of Technology, 2019) Özçeri İyikanat, Elif; Aygün, Gülnur; Tarhan, Enver; Tarhan, Enver; Aygün Özyüzer, Gülnur
Single-photon sources are essential components for several applications in the field of quantum information technologies, such as quantum cryptology and quantum computation. To this aim, efficient generation and detection of single-photons are the crucial to be achieved. Among single-photon sources that are extensively studied in the literature, defect centers in solid are very promising due to their room temperature operation and their stability. The aim of this thesis is to generate single photons at room temperature and control their optical properties by nanostructures. Single-photon emission from TMDCs originates from localized weakly bound excitons at cryogenic temperatures due to their small exciton binding energies. However, room temperature SP emission from WS2 can be obtained by creatingWO3 defects. In our study, room temperature emission from defects in WO3 was investigated. Density functional theory calculations showed that the source of the emission can be oxygen defects. Additionally, the emission was brightened by plasmonic gold nanoparticles. Furthermore, defects in two-dimensional (2D) hexagonal boron nitride (hBN) is offered as an efficient room temperature SPS. HBN is a wide bandgap 2D material, in which defect centers create discrete energy level to generate single photons. In our study, reversible single-photon emission control from defects in hBN was demonstrated by Förster-like resonance energy transfer between the single-photon emitter and a graphene layer. To this aim an ionic liquid based device structure was used.

Phd Degree / Doktora

Browse

Filters

Settings

Sort By

Results per page

Search Results