Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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

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Now showing 1 - 4 of 4
  • Master Thesis
    Graphene-Like Materials for Electronic Applications
    (01. Izmir Institute of Technology, 2020) Balcı, Sinan; Şahin, Hasan; Şahin, Hasan; Balcı, Sinan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Two-dimensional (2D) materials have gained vast interest in nanotechnology since these materials exhibit extraordinary properties due to electron confinement. Starting with graphene, many other 2D materials with characteristics of metals, semiconductors, insulators, and their magnetic analogues have been studied over the years. Insulators show importance as dielectric layers. Low dimensional metallic materials are used in electrical conduction. Ultra-thin semiconductors have variety of potential applications due to their characteristic band gap. Magnetic analogues of low dimensional materials are used in spintronics, offering high frequency, controllable switching. In addition, defects in these materials alter their physical properties and the concept can be adopted in order to use in different practices. Therefore it is important to study array of such materials and consider the alteration in their lattice theoretically and experimentally. In this thesis, first-principles calculations are used to predict insulating calcium halide single-layers are predicted, determine the effects of strain and V dopant in recently synthesized magnetic semiconducting VI3 single-layers, propose synthesis of magnetic, semiconducting manganese fluorides from manganese dichalcogenides, investigate the affects of defects and simulate scanning tunneling microscopy images in order to compare with experimental results, and finally to determine rather the detection of volatile organic compounds (VOC) such as methanol and ethanol by graphene-based sensors is feasible or not. Experiments are carried out to construct and further investigate the mechanism of VOC detection and working, highly sensitive alcohol sensors.
  • Master Thesis
    Flexible Transparent Conducting Electrodes Based on Silver Nanowire, Graphene, and Two-Dimensional Transition Metal Dichalgogenide
    (01. Izmir Institute of Technology, 2020) Balcı, Sinan; Balcı, Sinan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    In recent years, transparent conductive electrodes have attracted great interests owing to their critical applications in various optoelectronic devices, such as light emitting diodes, solar cells, liquid crystal displays, optical modulators, and touch screens. In this thesis, graphene-silver nanowires-transition metal dichalcogenide based hybrid transparent and conductive electrodes have been fabricated. In order to reach this goal; (1) single layer graphene on copper foil has been synthesized in large area in a CVD furnace, (2) ultrathin and very long silver nanowires have been synthesized by using wet chemistry methods, (3) MoS2 and WS2 single layer flakes and multilayer thin films have been synthesized in a CVD furnace, (4) electrodes of graphene, silver nanowires, and transition metal dichalcogenides have been fabricated on rigid and flexible substrates.
  • Master Thesis
    Investigation of Photodetectors Using Graphene Field Effect Transistors Incombination With Functional Dyematerials
    (Izmir Institute of Technology, 2020) Balcı, Sinan; Şahin, Hasan; Şahin, Hasan; Balcı, Sinan; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    A J-aggregate dye is a type of water-soluble, functional dye, which has a sharp and narrow absorption peak after it self-assembles into a brick-wall structure at high concentrations. The absorption peak of the J-aggregates is sharp, narrow and shifted to longer wavelengths compared to their monomer form and it is in the visible or near infrared spectrum. Due to its very sharp and narrow absorption, it has been used in silver halide photography, non-linear optics, lasing and sensing applications. On the other hand, graphene is one atom layer thick, honeycomb lattice of carbon atoms. In the pure, freestanding form, the bands of its electronic structure touch at one point, making it a gapless semimetal. Due to this characteristic, it is possible to manipulate its optical and electronic properties by changing the Fermi energy of graphene. Therefore, graphene found applications in many fields such as light emitting diodes, photodetectors, Hall sensors, optical modulators and flexible optoelectronics. The functional dye materials have not been combined with graphene photodetectors even though they are highly sensitive to light, less toxic than their competitors and stable at room temperature. In this thesis, using a J-aggregate dye, which has a sharp absorption peak around 585 nm wavelength, a graphene phototransistor has been demonstrated. By changing the charge concentration on graphene, using the charge carriers that arise from the excitation of J-aggregate dye, reversible modulation of graphene Dirac point has been demonstrated. In addition, a novel thin film formation technique has been developed in this study. Porous polyethylene membrane has been used to create thin films of water-soluble materials, such as J-aggregates, on hydrophobic surfaces.
  • Master Thesis
    Fabrication and Characterization of Graphene/Silicon Based Schottky Photodiode
    (Izmir Institute of Technology, 2019) Dönmez, Gülçin; Çelebi, Cem; Sarı, Emre; Çelebi, Cem; Sarı, Emre; 04.05. Department of Pyhsics; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    This thesis focused on fabrication and characterization of CVD grown p-type graphene and n-type Si Schottky junction photodiode with rectification behavior. The device operated at wavelength range between 390 and 1100 nm at self-powered mode. The device was encapsulated with Epoxy Resin to prevent graphene from atmospheric adsorbates. The electronic and optoelectronic characterizations of the devices were done before and after coating the devices with ER. By encapsulation stability of the device was enhanced in terms of photoresponsivity. The maximum obtained photoresponsivity value of the bare device was 0.56 A/W. Also, time-resolved photocurrent spectroscopy measurements showed that the devices exhibited enhanced photodetector performance in terms of photo-switching characteristics. Furthermore, electrical characteristics of Gr/n-Si Schottky photodiode under various illumination power densities with 850 nm wavelength were investigated. The short circuit current showed linear response to power density. However, open circuit voltage exhibited two phased slow and fast increment with increased power density. Hall effect measurements were conducted in order to investigate hole carrier concentration and mobility of the graphene on n-Si. With increasing the power density the carrier concentration increased and the mobility decreased. Besides, light induced manipulation of the Schottky barrier height of Gr/n-Si photodiode was studied. Schottky barrier height of the graphene measured by KPFM method as 0.4 eV. With increasing power density we found that Schottky barrier height of the device increased from 0.4 eV to 0.5 eV and showed similar trend with the change in open circuit voltage.