Physics / Fizik

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

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

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Now showing 1 - 3 of 3
  • Article
    Citation - WoS: 266
    Citation - Scopus: 292
    High Quality Ito Thin Films Grown by Dc and Rf Sputtering Without Oxygen
    (IOP Publishing Ltd., 2010) Tuna, Öcal; Özyüzer, Lütfi; Selamet, Yusuf; Selamet, Yusuf; Aygün, Gülnur; Aygün, Gülnur; Özyüzer, Lütfi; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technology
    High quality indium tin oxide (ITO) thin films were grown without oxygen by both dc and RF magnetron sputtering techniques on glass substrates. The effects of substrate temperature, film thickness and sputtering method on the structural, electrical and optical properties of the as-grown films were investigated. The results showed that the substrate temperature had substantial effects on the film properties, in particular on the crystallization and resistivity. When the substrate temperature was increased to 150 °C, crystallization in the (2 2 2) plane started appearing for both dc and RF sputtered films. We additionally found that with further increments of substrate temperature, the preferred crystallization orientation changed differently for dc and RF sputtered films. Optical transmission in the visible region for a film thickness of 70 nm was found to be above 85%. The bandgap was calculated to be about 3.64 eV for the substrate temperature of 150 °C for a 70 nm thick film. The value of the bandgap increased with respect to the increment in film thickness as well as substrate temperature. We also measured the temperature dependence of the resistivity and Hall coefficient of the films, and calculated the carrier concentration and Hall mobility. Very low room temperature resistivities for dc and RF magnetron sputtered grown films of about 1.28 × 10-4 Ω cm and 1.29 × 10-4 Ω cm, respectively, were obtained. © 2010 IOP Publishing Ltd.
  • 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.