Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
2 results
Search Results
Master Thesis Investigation of the Photo-Response of Graphene Silicon Photodetector in the Ultraviolet Region(01. Izmir Institute of Technology, 2024) Çelebi, Cem; Çelebi, Cem; Ünverdi, Özhan; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this thesis, we focus on the optoelectronic properties of p-type graphene and n-type Silicon (Gr/Si) Schottky barrier photodiode according to the number of layers in the ultraviolet region (UV). The I-V measurements were conducted at an applied bias voltage between -0.5 and 0.5 V for each Gr/Si heterojunction. The I-V measurements taken under dark conditions showed that all Gr/Si samples with 2-, 4- and 6-layers graphene electrodes exhibited rectifying Schottky junction character, but all device's reverse saturation currents (I0) were different. Schottky barrier heights (ΦB) of the samples with 2-, 4- and 6-layers graphene electrodes were determined using the I0 values obtained from I-V measurements. Compared to the ΦB value of the sample with 2 layers graphene electrode, the ΦB of the sample with 4 layers of graphene electrode increased to ~0.82 eV, and then ΦB was found to decrease to ~0.79 eV for the 6-layer graphene electrode. Additionally, photo-response measurements were carried out at zero bias voltage and in the wavelength range of 250 – 400 nm to determine the spectral response (R) of the devices in the UV region. Compared to the device with 2 layers graphene electrode, R of the sample with 4 layers graphene electrode increased by 3 times. The result obtained revealed that using 4-layer graphene as a light-transparent electrode, Gr/Si Schottky barrier photodiode is the most applicable option for sensitive detection of light in the UV region.Master Thesis Nanotribological Properties of Graphene Grown on Silicon Carbide Semiconductor(Izmir Institute of Technology, 2018) Keskin, Yasemin; Çelebi, Cem; Çelebi, Cem; Ünverdi, Özhan; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this thesis, nanotribological properties of single and multilayer graphene grown on two sides of the Silicon Carbide (SiC) semiconductors were investigated. For this purpose, epitaxial growth technique was used to obtain single-layer graphene on both C-face and Si-face. This thesis consists of two purposes: One of them is to investigate the nanotribological properties of the single and multilayer graphene grown on C-face of SiC and the other one is to compare nanotribological properties of the single layer graphene on two sides of SiC. Graphene, a two-dimensional semi-metal material, was grown epitaxially on the SiC surface under ultra-high vacuum conditions. In epitaxial method, direct current heating is applied to the SiC substrate to vaporize Si atoms from the surface. As the Si atoms evaporate, the remaining C atoms form a graphene layers on top. When single layer graphene is formed on the Si-face, multilayer graphene is formed on the C-face at the same parameters. For this reason, two different samples of graphene were needed in order to compare the tribological properties of the single layer graphene grown on both Si-face and C-face for the secondary objective. A capping method was used to control the rate of Si atoms evaporating from the SiC surface. By this way, single layer graphene on the C-face was obtained too. Number of layers were determined by Raman Spectroscopy. Nanotribological characterizations were done with Atomic Force Microscopy. The experimental results showed that single layer graphene on the Si-face has higher friction coefficient compared to single layer graphene on the C-face. It has been found that the single layer graphene (0.02) formed on the C-surface has a lower coefficient of friction than the multilayer graphene (0.82). It is expected that with the support of the theoretical studies on this results will increase the interest in this study by means of these results are new and original for the literature.