Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

Browse

Filters

2004 - 200922010 - 20181

Settings

Author: search.filters.author.Özyüzer, Gülnur AygünPublisher: search.filters.publisher.IOP Publishing Ltd.

Search Results

Now showing 1 - 3 of 3
  • Article
    Citation - WoS: 42
    Citation - Scopus: 46
    Importance of Cds Buffer Layer Thickness on Cu2znsns4-Based Solar Cell Efficiency
    (IOP Publishing Ltd., 2018) Cantaş, Ayten; Türkoğlu, Fulya; Aygün, Gülnur; Akça, Fatime Gülşah; Özdemir, Mehtap; Tarhan, Enver; Özyüzer, Lütfi; Özyüzer, Gülnur Aygün; Özdemir, Mehtap; Özyüzer, Lütfi; Tarhan, Enver; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Cu2ZnSnS4 (CZTS) thin films were grown on Mo-coated soda lime glass (SLG) substrates by the sulfurization of DC magnetron-sputtered Zn, Sn and Cu metallic precursors under a sulfur atmosphere at 550 °C for 45 min. Understanding the composition and structure of the CZTS absorber layer is necessary to obtain efficient solar cells. With this aim, x-ray diffractometry, Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy and x-ray photoelectron spectroscopy were used to investigate the CZTS absorber layers. CZTS absorber films were obtained and found to be Cu-poor and Zn-rich in composition, which are both qualities desired for efficient solar cells. CdS was used as a buffer layer and was grown by the chemical bath deposition technique. The optical properties of CdS films on SLG were searched for using a spectroscopic ellipsometer and the results revealed that the bandgap increases with film thickness increment. CZTS-based solar cells with different CdS buffer layer thicknesses were prepared using a SLG/Mo/CZTS/CdS/ZnO/AZO solar cell configuration. The influence of the CdS buffer layer thickness on the performance of the CZTS solar cells was investigated. Device analysis showed that electrical characteristics of solar cells strongly depend on the buffer layer's thickness. Highly pronounced changes in V OC, fill factor and J SC parameters, which are the main efficiency limiting factors, with changing buffer layer thicknesses were observed. Our experiments confirmed that decreasing the CdS thickness improved the efficiency of CZTS solar cells down to the lowest thickness limit.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 15
    Local Oxidation Nanolithography on Hf Thin Films Using Atomic Force Microscopy (afm)
    (IOP Publishing Ltd., 2009) Büyükköse, Serkan; Okur, Salih; Okur, Salih; Aygün, Gülnur; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Well controlled Hf oxide patterns have been grown on a flat Hf thin film surface produced by the dc magnetron sputtering method on Si and SiOx substrates. These patterns have been created by using the technique of semi-contact scanning probe lithography (SC-SPL). The thickness and width of the oxide patterns have been measured as a function of applied voltage, duration and relative humidity. There is a threshold voltage even at 87% humidity, due to insufficient energy required to start the oxide growth process for a measurable oxide protrusion. Electrical characterization was also performed via the I-V curves of Hf and HfOx structures, and the resistivity of HfO x was found to be 4.284 × 109 Ω cm. In addition to the I-V curves, electric force microscopy and spreading surface resistance images of Hf and HfOx were obtained.
  • Article
    Citation - WoS: 22
    Citation - Scopus: 22
    Oxidation of Si Surface by a Pulsed Nd: Yag Laser
    (IOP Publishing Ltd., 2004) Özyüzer, Gülnur Aygün; Atanassova, Elenada A.; Aygün, Gülnur; Özyüzer, Lütfi; Turan, Raşit; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    SiO2 thin films have been obtained by 1064 nm Nd: YAG laser oxidation of p-Si in the presence of O2. The thickness uniformity, dielectric and electrical properties of the layers have been studied. The effect of both the laser beam energy density and the substrate temperature on the oxide growth is also discussed. It was established that there exists an interval of laser beam energy density in which the oxidation occurs without surface melting. The oxidation process is controlled by the laser beam energy density rather than by the substrate temperature (673-748 K) and the higher laser power results in a thicker oxide. X-ray photoelectron spectroscopy (XPS) was used to provide information on the oxide composition. XPS results revealed that the as-grown oxide is a mixed layer of SiO2 and Si2O, which are distributed nonuniformly through the depth. MOS capacitors fabricated on the grown oxide exhibited typical capacitance-voltage, conductance-voltage characteristics. However, the density of interface states and oxide charge density were found to be higher than the typical values of thermally grown oxides. The quality of the oxide layers can be further improved by optimization of the process parameters and/or by post-processing of the grown films. It is concluded that the SiO2 films formed by the technique of Nd: YAG laser-enhanced oxidation at low temperature are potentially useful for device applications.