WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 15Citation - Scopus: 17Effect of Substrate Rotation Speed and Off-Center Deposition on the Structural, Optical, and Electrical Properties of Azo Thin Films Fabricated by Dc Magnetron Sputtering(American Institute of Physics, 2018) Aygün, Gülnur; Aygün, Gülnur; Köseoğlu, Hasan; Özdemir, Mehtap; Özdemir, Mehtap; Özyüzer, Lütfi; Özyüzer, Lütfi; Özyüzer, Gülnur Aygün; Özyüzer, Lütfi; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this study, aluminum-doped zinc oxide (AZO) thin films were deposited by DC magnetron sputtering at room temperature. The distance between the substrate and target axis, and substrate rotation speed were varied to get high quality AZO thin films. The influences of these deposition parameters on the structural, optical, and electrical properties of the fabricated films were investigated by X-ray diffraction (XRD), Raman spectroscopy, spectrophotometry, and four-point probe techniques. The overall analysis revealed that both sample position and substrate rotation speed are effective in changing the optical, structural, and electrical properties of the AZO thin films. We further observed that stress in the films can be significantly reduced by off-center deposition and rotating the sample holder during the deposition. An average transmittance above 85% in the visible range and a resistivity of 2.02 × 10-3Ω cm were obtained for the AZO films.Article Citation - WoS: 10Citation - Scopus: 10In-Situ Spectroscopic Ellipsometry and Structural Study of Hfo2 Thin Films Deposited by Radio Frequency Magnetron Sputtering(American Institute of Physics, 2014) Cantaş, Ayten; Özyüzer, Gülnur Aygün; Aygün, Gülnur; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe have investigated the reduction of unwanted interfacial SiO2 layer at HfO2/Si interface brought about by the deposition of thin Hf metal buffer layer on Si substrate prior to the deposition of HfO2 thin films for possible direct contact between HfO2 thin film and Si substrate, necessary for the future generation devices based on high-κ HfO2 gate dielectrics. Reactive rf magnetron sputtering system along with the attached in-situ spectroscopic ellipsometry (SE) was used to predeposit Hf metal buffer layer as well as to grow HfO2 thin films and also to undertake the in-situ characterization of the high-κ HfO2 thin films deposited on n-type 〈100〉 crystalline silicon substrate. The formation of the unwanted interfacial SiO2 layer and its reduction due to the predeposited Hf metal buffer layer as well as the depth profiling and also structure of HfO2 thin films were investigated by in-situ SE, Fourier Transform Infrared spectroscopy, and Grazing Incidence X-ray Diffraction. The study demonstrates that the predeposited Hf metal buffer layer has played a crucial role in eliminating the formation of unwanted interfacial layer and that the deposited high-κ HfO2 thin films are crystalline although they were deposited at room temperature.Article Citation - WoS: 15Citation - Scopus: 13Impact of temperature increments on tunneling barrier height and effective electron mass for plasma nitrided thin Sio2 layer on a large wafer area(American Institute of Physics, 2010) Aygün, Gülnur; Aygün, Gülnur; Erlbacher, T.; Wolf, M.; Schellenberger, M.; Pfitzner, L.; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyThermally grown SiO2 layers were treated by a plasma nitridation process realized in a vertical furnace. The combination of a pulsed-low frequency plasma and a microwave remote plasma with N2/NH 3/He feed gas mixture was used to nitride the thermally grown SiO2 gate dielectrics of MIS structures. Temperature dependency of effective masses and the barrier heights for electrons in pure thermally grown SiO2 as well as plasma nitrided SiO2 in high electric field by means of Fowler-Nordheim regime was determined. It is frequently seen from the literature that either effective electron mass or barrier height (generally effective electron mass) is assumed to be a constant and, as a result, the second parameter is calculated under the chosen assumption. However, in contrast to general attitude of previous studies, this work does not make any such assumptions for the calculation of neither of these two important parameters of an oxide at temperature ranges from 23 to 110 °C for SiO 2, and 23 to 130 °C for nitrided oxide. It is also shown here that both parameters are affected from the temperature changes; respectively, the barrier height decreases while the effective mass increases as a result of elevated temperature in both pure SiO2 and plasma nitrided SiO 2. Therefore, one parameter could be miscalculated if the other parameter, i.e., effective mass of electron, was assumed to be a constant with respect to variable physical conditions like changing temperature. Additionally, the barrier heights were calculated just by taking constant effective masses for both types of oxides to be able to compare our results to common literature values. © 2010 American Institute of Physics.Article Citation - WoS: 59Citation - Scopus: 59Interfacial and Structural Properties of Sputtered Hfo2 Layers(American Institute of Physics, 2009) Özyüzer, Gülnur Aygün; Aygün, Gülnur; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyMagnetron sputtered HfO2 layers formed on a heated Si substrate were studied by spectroscopic ellipsometer (SE), x-ray diffraction (XRD), Fourier transform infrared (FTIR), and x-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO x suboxide layer at the HfO2 /Si interface is unavoidable. The HfO2 thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O2 /Ar gas ratio during sputtering, sputtering time, and substrate temperature. XRD spectra show that the deposited film has (111) monoclinic phase of HfO2, which is also supported by FTIR spectra. The atomic concentration and chemical environment of Si, Hf, and O have been measured as a function of depth starting from the surface of the sample by XPS technique. It shows that HfO2 layers of a few nanometers are formed at the top surface. Below this thin layer, Si-Si bonds are detected just before the Si suboxide layer, and then the Si substrate is reached during the depth profiling by XPS. It is clearly understood that the highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO2 to form HfO2, leaving Si-Si bonds behind.