Browsing by Author "Ozcelik, Suleyman"

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Citation - WoS: 9
Citation - Scopus: 11
Chemical Bonding Structure of Tio2 Thin Films Grown on N-Type Si
(Elsevier Science Sa, 2011) Baleanu, Cristina-Mihaela; Nigmatullin, Raoul R.; Baleanu, Dumitru; Ozcelik, Suleyman; Cetin, S. Sebnem; 115476; 8762; 02.02. Matematik; 02. Fen-Edebiyat Fakültesi; 01. Çankaya Üniversitesi
Titanium dioxide thin films were obtained by RF magnetron sputtering system with different Ar and O atmospheres. Chemical bonding structures of the thin films were investigated using the Fourier transform infrared spectroscopy (FTIR) in the range of 400-7500 cm(-1) for as-deposited and conventionally thermal annealed films at different temperature in air. These structural characterizations of the films were carried out by describing the low-frequency fluctuations of the FTIR spectra using the noninvasive (i.e. error controllable) procedure of the optimal linear smoothing. This approach is based on the criterion of the minimal relative error in selection of the proper smoothing window. It allows the receiving an optimal separation of a possible trend from the high-frequency fluctuations, defined as a random sequence of the relative fluctuations possessing zero trends. Thus, the noise can be read and extra information about the structures was then obtained by comparing with the experimental results. In the film annealed at 900 degrees C, the rutile phase was the dominant crystalline phase as revealed by infrared spectroscopy. At the annealing temperatures lower than 900 degrees C, both the anatase and the rutile phases were coexisting. In addition, symmetric and asymmetric Si-O-Si vibrations modes were observed at around 1000 cm(-1) and 800 cm(-1), respectively. These peaks suggest that a thin SiO2 film was formed at the TiO2/Si interface during the growth and the annealing of the TiO2 films. It was also observed that the reactivity between TiO2 film and Si substrate is increased with the increasing annealing temperature. (C) 2011 Elsevier B.V. All rights reserved.
Citation - WoS: 8
Citation - Scopus: 8
New Method and Treatment Technique Applied To Interband Transition in Gaas1-Xpx Ternary Alloys
(versita, 2011) Nigmatullin, Raoul R.; Cetin, Saime Sebnem; Baleanu, Dumitru; Ozcelik, Suleyman; Baleanu, Cristina-Mihaela; 56389; 02.02. Matematik; 02. Fen-Edebiyat Fakültesi; 01. Çankaya Üniversitesi
In this paper we presented a new method (Eigen-Coordinates (ECs)) that can be used for calculations of the critical points (CPs) energy of the interband-transition edges of the heterostructures. This new method is more accurate and complete in comparison with conventional ones and has a wide range of application for the calculation of the fitting parameters related to nontrivial functions that initially have nonlinear fitting parameters that are difficult to evaluate. The new method was applied to determine the CPs energies from the dielectric functions of the MBE grown GaAs1-xP (x) ternary alloys obtained using spectroscopic ellipsometry (SE) measurements at room temperature in the 0.5-5 eV photon energy region. The obtained results are in good agreement with the results of the other methods.
Citation - WoS: 1
Citation - Scopus: 1
Structures and Energetics of Cu21-Cu71 Clusters: a Molecular Dynamics Study
(Gazi Univ, 2009) Güvenç, Ziya Burhanettin; Cetin, Saime Sebnem; Ozcelik, Suleyman; Guvenc, Ziya B.; Bilgisayar Mühendisliği; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Using Molecular Dynamics and thermal quenching simulations the stable geometrical structures and energies of Cun (n=21-71) clusters are identified. The interaction between the cluster atoms is modeled by an EmbeddedAtom Potential Surface, Voter and Chen's version. The stable geometrical structures and energies are obtained from 500 phase space coordinates generated along high-energy trajectories. The internal energy (about T=2500 K) is above the melting temperature of the Cun clusters. The thermal quenching technique is employed to remove slowly the internal kinetic energy of the clusters. Because of this slow minimization process the locally stable isomers are separated from those meta-stable ones.