Browsing by Author "Özdoğan, Cem"

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About nanometer sized analogues of basic electronic and optical components
(IEEE, 2008) Quandt, Alexander; Özdoğan, Cem; Ferrari, Maurizio; Speranza, Giorgio
We discuss a downsizing of optical components into the nanometer range. It presupposes the substitution of photons by ballistic electrons, but it also requires a simple and robust concept to assemble the analogues of basic electronic and optical components on such a tiny length scale. Here, one of the most promising candidate schemes employs graphene as a basic nanosubstrate. We elucidate the suggested behaviour of graphene as an electronic metamaterial [1], and show that other desired electronic or optical functionalities may be obtained through a patterning with sub-nanometer sized boron clusters [2].
Citation - WoS: 3
Citation - Scopus: 6
Hydrogen Hosting of Nano Scale Boron Clusters
(Editura Acad Romane, 2008) Özdoğan, Cem; Bäoyäukata, M.; ÄozdoGan, C.; Gäuvenc, Z.B.; Ortak Dersler Bölümü
In this paper the Density Functional Results of hydrogen bonded boron micro clusters with B3LYP/6-311++G(d,p) level of computations will be presented. Energetics and structural stability with their possible stable geome- tries of various selected micro complexes of BmHn (for m and n<11) boron hydrides have been analysed, and their binding energies with HOMO-LUMO energy gaps have been determined. Mainly, e®ects of the number of hydrogen atoms on the structures of the boranes are assessed. Moreover, for the cage con̄gurations their distortions have been investigated for the neutral, anionic and cationic cases. It has been observed that there have been two opposing factors for the cage con̄gurations. One of which is the \peeling' of the cage structures by the hydrogen atoms, and the other one is reforming a smaller cage form simultaneously with the remaining boron atoms inside. This is observed mostly for the odd values of m. From our studies it has been also observed that with the bare boron clusters alone, it is di±cult to increase the capacity of the hydrogen storage. Therefore, further studies are necessary with the boron complexes.
Nanotüplerin Elektronik Yapısının ve Bunun Topolojik Kusurlar ve Gerilmeler Altındaki Değişiminin Sıcaklığa Bağlı Bilgisayar Simulasyonu
(2001) Özdoğan, Cem; Dereli, Gülay; Çağın, Tahir
Karbon nanotüp simulasyonlarında kullanılmak üzere N-mertebeli, paralel hesap tekniği kullanılan sıkı bağ moleküler dinamik simulasyon programı geliştirilmiştir. geliştirilen algoritma , Comp. Phys. Comm. 148(2002)'de basılmıştır. Geliştirilen algoritma kullanılarak oluşturulan değişik geometrilere sahip karbon nanotüplerin elektronik yapıları ile elastik/plastik yapıları oda sıcaklığında germeler ve sıkıştırmalar altında incelenmiş sonuçlar Phys. Rev.'de basılmıştır.
Structural stability and energetics of single-walled carbon nanotubes under uniaxial strain
(2003) Dereli, G.; Özdoğan, Cem
A (10x10) single-walled carbon nanotube consisting of 400 atoms with 20 layers is simulated under tensile loading using our developed O(N) parallel tight-binding molecular-dynamics algorithms. It is observed that the simulated carbon nanotube is able to carry the strain up to 122% of the relaxed tube length in elongation and up to 93% for compression. Young's modulus, tensile strength, and the Poisson ratio are calculated and the values found are 0.311 TPa, 4.92 GPa, and 0.287, respectively. The stress-strain curve is obtained. The elastic limit is observed at a strain rate of 0.09 while the breaking point is at 0.23. The frequency of vibration for the pristine (10x10) carbon nanotube in the radial direction is 4.71x10(3) GHz and it is sensitive to the strain rate.
Surface modification by 1 keV ion impact: molecular dynamics study of an Ar+-Ni(100) collision system
(IOP Publishing Ltd, 2008) Özdoğan, Cem; Atis, Murat; Güvenç, Ziya B.
An Ar+-Ni(1 0 0) collision system at 1 keV impact energy was investigated by using realistic isoenergetic molecular dynamics (MD) simulations. The sputtering process upon Ar+ ion impact and damage to the Ni(1 0 0) surface are examined in detail. Studying of high bombarding energy regions leads to the necessity of larger and thick enough slabs, otherwise incoming ions can easily pass through the slab; as a result, investigated physical properties may not be revealed. In addition the simulation time should be long enough to observe and to calculate a reliable macroscopic property such as sputtering yield that is addressed in this study. In order to preserve the total energy in the simulation at this collision energy a small time-step (0.1 fs) is used. We have made use of our developed linear scaling parallel MD program to overcome these demands. The Ni(1 0 0) slab is formed by 63700 atoms (122 angstrom x 122 angstrom x 44 angstrom) and the total observation time for each collision event is about 2.25 ps. Several properties such as penetration depths, angular and energy distributions of the reflected Ar and sputtered Ni atoms as well as dissociation time, embedded, scattering, sputtering patterns and geometries of the sputtered clusters are also reported, and the calculated sputtering yield is found to be in good agreement with the available experimental results.
Temiz Enerji Kaynağı Hidrojenin Nano Yapılarda Depolanması
(2007) Büyükata, Mustafa; Atiş, Murat; Güvenç, Ziya B.; Özdoğan, Cem