Now showing items 1-20 of 91

    • Ab initio study of Ru-terminated and Ru-doped armchair graphene nanoribbons 

      Sarikavak-Lisesivdin, B.; Lisesivdin, S. B.; Ozbay, E. (Taylor and Francis, 2012)
      We investigate the effects of ruthenium (Ru) termination and Ru doping on the electronic properties of armchair graphene nanoribbons (AGNRs) using first-principles methods. The electronic band structures, geometries, density ...
    • Adsorption of group IV elements on graphene, silicene, germanene and stanene: dumbbell formation 

      Ozcelik, V. O.; Kecik, D.; Durgun, E.; Ciraci, S. (ACS Publications, 2014-12-09)
      Silicene and germanene derivatives constructed from periodic dumbbell units play a crucial role in multilayers of these honeycomb structures. Using first-principles calculations based on density functional theory, here ...
    • All-fiber Yb-doped laser mode-locked by nanotubes 

      Zhang, U.Z.; Popa, D.; Sun, Z.; Hasan, T.; Ferrari, A.C.; Ilday F.O. (IEEE Computer Society, 2013)
      Single-wall carbon nanotubes (SWNTs) and graphene have emerged as promising saturable absorbers (SAs), due to their broad operation bandwidth and fast recovery times [1-3]. However, Yb-doped fiber lasers mode-locked using ...
    • Broadband optical modulators based on graphene supercapacitors 

      Polat, E. O.; Kocabas, C. (American Chemical Society, 2013)
      Optical modulators are commonly used in communication and information technology to control intensity, phase, or polarization of light. Electro-optic, electroabsorption, and acousto-optic modulators based on semiconductors ...
    • Broadband terahertz modulators using self-gated graphene capacitors 

      Kakenov, N.; Balci, O.; Polat, E. O.; Altan, H.; Kocabas, C. (Optical Society of America, 2015)
      We demonstrate a terahertz intensity modulator using a graphene supercapacitor which consists of two large-area graphene electrodes and an electrolyte medium. The mutual electrolyte gating between the graphene electrodes ...
    • Broadband THz modulators based on multilayer graphene on PVC 

      Kaya E.; Kakenov N.; Kocabas C.; Altan H.; Esenturk O. (IEEE Computer Society, 2016)
      In this study we present the direct terahertz time-domain spectroscopic measurement of CVD-grown multilayer graphene (MLG) on PVC substrate with an electrically tunable Fermi level. In a configuration consisting MLG and ...
    • Comparison of back and top gating schemes with tunable graphene fractal metasurfaces 

      Aygar, A. M.; Balci, O.; Cakmakyapan, S.; Kocabas, C.; Caglayan, H.; Ozbay, E. (American Chemical Society, 2016)
      In this work, fractal metasurfaces that consist of periodic gold squares on graphene are used to increase light-graphene interaction. We show by simulations and experiments that higher level fractal structures result in ...
    • Compressive sensing imaging with a graphene modulator at THz frequency in transmission mode 

      Ozkan V.A.; Takan T.; Kakenov N.; Kocabas C.; Altan H. (IEEE Computer Society, 2016)
      In this study we demonstrate compressive sensing imaging with a unique graphene based optoelectronic device which allows us to modulate the THz field through an array of columns or rows distributed throughout its face. © ...
    • Controlling phase of microwaves with active graphene surfaces 

      Balci O.; Kakenov N.; Kocabas C. (American Institute of Physics Inc., 2017)
      In this letter, we report a method to control the reflection phase of microwaves using electrically tunable graphene devices. The device consists of mutually gated large-area graphene layers placed at a quarter-wave distance ...
    • Controlling the photoconductivity: graphene oxide and polyaniline self assembled intercalation 

      Vempati S.; Ozcan, S.; Uyar T. (American Institute of Physics Inc., 2015)
      We report on controlling the optoelectronic properties of self-assembled intercalating compound of graphene oxide (GO) and HCl doped polyaniline (PANI). Optical emission and X-ray diffraction studies revealed a secondary ...
    • Coupling enhancement of split ring resonators on graphene 

      Cakmakyapan, S.; Caglayan, H.; Ozbay, E. (Pergamon Press, 2014-12)
      Metallic split ring resonator (SRR) structures are used in nanophotonics applications in order to localize and enhance incident electromagnetic field. Electrically controllable sheet carrier concentration of graphene ...
    • DFT studies of graphene-functionalised derivatives of capecitabine 

      Aramideh, M.; Mirzaei, M.; Khodarahmi, G.; Gülseren, O. (Walter de Gruyter GmbH, 2017-10)
      Cancer is one of the major problems for so many people around the world; therefore, dedicating efforts to explore efficient therapeutic methodologies is very important for researchers of life sciences. In this case, ...
    • Dynamic tuning of plasmon resonance in the visible using graphene 

      Balci, S.; Balci, O.; Kakenov, N.; Atar, F. B.; Kocabas, C. (The Optical Society, 2016)
      We report active electrical tuning of plasmon resonance of silver nanoprisms (Ag NPs) in the visible spectrum. Ag NPs are placed in close proximity to graphene which leads to additional tunable loss for the plasmon resonance. ...
    • Effective mass of electron in monolayer graphene: Electron-phonon interaction 

      Tiras, E.; Ardali, S.; Tiras, T.; Arslan, E.; Cakmakyapan, S.; Kazar, O.; Hassan, J.; Janzén, E.; Ozbay, E. (AIP Publishing LLC, 2013-01-25)
      Shubnikov-de Haas (SdH) and Hall effect measurements performed in a temperature range between 1.8 and 275 K, at an electric field up to 35 kV m -1 and magnetic fields up to 11 T, have been used to investigate the electronic ...
    • Effects of charging on two-dimensional honeycomb nanostructures 

      Topsakal, Mehmet (Bilkent University, 2012)
      In this thesis we employ state-of-the-art first-principles calculations based on density functional theory (DFT) to investigate the effects of static charging on two-dimensional (2D) honeycomb nanostructures. Free standing, ...
    • Effects of silicon and germanium adsorbed on graphene 

      Aktürk, E.; Ataca, C.; Ciraci, S. (A I P Publishing LLC, 2010)
      Based on the first-principles plane wave calculations, we studied the adsorption of Si and Geon graphene. We found that these atoms are bound to graphene at the bridge site with a significant binding energy, while many ...
    • Electrically controlled terahertz spatial light modulators with graphene arrays 

      Kakenov, N.; Takan, T.; Ozkan, V. A.; Balci, O.; Polat, E. O.; Altan, H.; Kocabas, C. (Institute of Electrical and Electronics Engineers Inc., 2016)
      Gate-tunable high-mobility electrons on atomically thin graphene layers provide a unique opportunity to control electromagnetic waves in a very broad spectrum. In this paper, we describe an electrically-controlled multipixel ...
    • Electronic structure of graphene nano-ribbons 

      Şen, Hüseyin Şener (Bilkent University, 2008)
      Graphite is a known material to human kind for centuries as the lead of a pencil. Graphene as a two dimensional material, is the single layer of graphite. Many theoretical works have been done about it so far, however, ...
    • Electronic structure of graphene under the influence of external fields 

      İslamoğlu, Selcen (Bilkent University, 2012)
      In this thesis, the electronic structure of graphene under the influence of external fields such as strain or magnetic fields is investigated by using tight-binding method. Firstly, we study graphene for a band gap opening ...
    • Electrostatic energy barriers from dielectric membranes upon approach of translocating DNA molecules 

      Buyukdagli S.; Ala-Nissila T. (A I P Publishing LLC, 2016)
      We probe the electrostatic cost associated with the approach phase of DNA translocation events. Within an analytical theory at the Debye-Hückel level, we calculate the electrostatic energy of a rigid DNA molecule interacting ...