Now showing items 1-20 of 32

    • Accurate method for obtaining band gaps in conducting polymers using a DFT/hybrid approach 

      Salzner, U.; Pickup, P. G.; Poirier, R. A.; Lagowski, J. B. (American Chemical Society, 1998)
      DFT calculations on a series of oligomers have been used to estimate band gaps, ionization potentials, electron affinities, and bandwidths for polyacetylene, polythiophene, polypyrrole, polythiazole, and a thiophene - ...
    • Accurate modeling of metamaterials with MLFMA 

      Ergül Ö.; Ünal, A.; Gürel, L. (2006)
      Electromagnetic modelling of large metamaterial (MM) structures employing multilevel fast multipole algorithm (MLFMA) is reported. MMs are usually constructed by periodically embedding unit cells, such as split-ring ...
    • Band gap and optical transmission in the Fibonacci type one-dimensional A5B6C7 based photonic crystals 

      Simsek S.; Koc, H.; Palaz S.; Oltulu, O.; Mamedov, A. M.; Özbay, Ekmel (Wiley-VCH Verlag, 2015)
      In this work, we present an investigation of the optical properties and band structure calculations for the photonic crystal structures (PCs) based on one-dimensional (1D) photonic crystal. Here we use 1D A5B6C7(A:Sb; ...
    • Band Structure and Optical Properties of Kesterite Type Compounds: First principle calculations 

      Palaz S.; Unver H.; Ugur G.; Mamedov, Amirullah; Özbay, Ekmel (Institute of Physics Publishing, 2017)
      In present work, our research is mainly focused on the electronic structures, optical and magnetic properties of Cu2FeSnZ4 (Z = S, Se) compounds by using ab initio calculations within the generalized gradient approximation ...
    • Band-dropping via coupled photonic crystal waveguides 

      Bayindir, M.; Özbay, Ekmel (Optical Society of American (OSA), 2002)
      We observe the dropping of electromagnetic waves having a specific frequency or a certain frequency band in two-dimensional dielectric photonic crystals. The single frequency is dropped via cavity-waveguide coupling. ...
    • Chiral single-wall gold nanotubes 

      Senger, R. T.; Dag, S.; Ciraci, S. (American Physical Society, 2004)
      The formation of freestanding and tip-suspended chiral-wall (n,m) nanotubes, which were composed of helical atomic strands, from gold atoms was investigated using first-principles calculations, where (n,m) notation defines ...
    • Determination of energy-band offsets between GaN and AlN using excitonic luminescence transition in AlGaN alloys 

      Westmeyer, A. N.; Mahajan, S.; Bajaj, K. K.; Lin J. Y.; Jiang, H. X.; Koleske, D. D.; Senger, R. T. (American Institute of PhysicsA I P Publishing LLC, 2006)
      We report the determination of the energy-band offsets between GaN and AlN using the linewidth (full width at half maximum) of an extremely sharp excitonic luminescence transition in Alx Ga1-x N alloy with x=0.18 at 10 K. ...
    • Electron initiated impact ionization in AlGaN alloys 

      Bulutay, C. (Institute of Physics, 2002)
      Detailed impact ionization (II) analysis of electrons is presented for AlGaN alloys as a vital resource for solar-blind avalanche photodiode and high power transistor applications. Necessary ingredients for the II ...
    • Enhanced hole transport in InGaN/GaN multiple quantum well light-emitting diodes with a p-type doped quantum barrier 

      Ji Y.; Zhang, Z. -H.; Tan S.T.; Ju, Z. G.; Kyaw, Z.; Hasanov N.; Liu W.; Sun X. W.; Demir, Hilmi Volkan (Optical Society of America, 2013)
      We study hole transport behavior of InGaN/GaN light-emitting diodes with the dual wavelength emission method. It is found that at low injection levels, light emission is mainly from quantum wells near p-GaN, indicating ...
    • Functionalized carbon nanotubes and device applications 

      Ciraci, S.; Dag, S.; Yildirim, T.; Gülseren, O.; Senger, R. T. (Institute of Physics Publishing Ltd., 2004)
      Carbon nanotubes, in which the two-dimensional hexagonal lattice of graphene is transformed into a quasi-one-dimensional lattice by conserving the local bond arrangement, provide several structural parameters for engineering ...
    • Low dark current N structure superlattice MWIR photodetectors 

      Salihoglu, O.; Muti, A.; Turan, R.; Ergun, Y.; Aydinli, A. (SPIE, 2014)
      Commercially available read out integrated circuits (ROICs) require the FPA to have high dynamic resistance area product at zero bias (R0A) which is directly related to dark current of the detector. Dark current arises ...
    • Low-temperature photoluminescence spectra of layered semiconductor TlGaS2 

      Gasanly, N. M.; Aydinli, A.; Bek, A.; Yilmaz, I. (Pergamon Press, 1998)
      Photoluminescence (PL) spectra of TlGaS2 layered single crystals were studied in the wavelength region 500-860 nm and in the temperature range 9.5-293 K. We observed a total of three PL bands centered at 568 nm (2.183 eV, ...
    • Low-temperature photoluminescence spectra of TlInxGa1-xS2 layer mixed crystals 

      Allakhverdiev, K. R.; Gasanly, N. M.; Aydinli, A. (Pergamon Press, 1995)
      Low-temperature photoluminescence spectra of TlInS2, TlIn0.95Ga0.05S2 and TlIn0.8Ga0.2S2 layer crystals were studied in the temperature range 14-220 K. The temperature dependencies of bands 2.374 eV (A), 2.570 eV (E) and ...
    • Low-temperature visible photoluminescence spectra of TlGaSe2 layered crystal 

      Gasanly, N. M.; Serpengüzel, A.; Aydınlı, A.; Baten, S. M. A. (Elsevier Science Publishers B.V., Amsterdam, Netherlands, 2000)
      The photoluminescence (PL) spectra of TlGaSe2 layered single crystals were investigated in the 8.5-35 K temperature. 0.2-15.2 W cm-2 excitation laser intensity, and in the 600-700 nm wavelength range. The PL spectrum has ...
    • Magic gold nanotubes 

      Senger, R.T.; Daǧ, S.; Çiraci, S. (2005)
      In recent ultra-high-vacuum transmission-electron-microscopy experiments evidence is found for the formation of suspended gold single-wall nanotubes (SWNTs) composed of five helical strands. Similar to carbon nanotubes, ...
    • One and two dimensional LiNbO3 photonic crystals 

      Şimşek, Şevket; Mamedov, Amirullah M.; Özbay, Ekmel (IEEE, 2013)
      In this report, we present an investigation of the optical properties and band structure calculations for the photonic crystal structures (PCs) based on one-dimensional (1D) and two-dimensional (2D) ferroelectric LiNbO3 ...
    • Optical, electronic, and elastic properties of some A5B6C7 ferroelectrics (A=Sb, Bi; B=S, Se; C=I, Br, Cl): first principle calculation 

      Koc, H.; Palaz S.; Mamedov, A. M.; Özbay, Ekmel (Taylor and Francis Inc., 2017)
      In present paper, we focus on the structural, mechanical, electronic, and optical properties for the A5B6C7(A = Sb, Bi; B = Te, Se; S; C = I, Br, Cl) compounds using the density functional methods in generalized gradient ...
    • Pseudopotential-based full zone k · p technique for indirect bandgap semiconductors: Si, Ge, diamond and SiC 

      Bulutay, C. (2006)
      The k · p is a versatile technique that describes the semiconductor band structure in the vicinity of the bandgap. The technique can be extended to full Brillouin zone by including more coupled bands into consideration. ...
    • Quantum transport through one-dimensional aluminum wires 

      Batra, I. P.; Sen, P.; Ciraci, S. (AIP Publishing, 2002)
      Quantum conductance in narrow channels has been well understood by using the two-dimensional electron gas, a model system which has been realized in semiconductor heterojunctions. An essential property of this electron ...
    • Radiative donor-acceptor pair recombination in TlInS2 single crystals 

      Aydınlı, A.; Gasanly, N. M.; Yılmaz, I.; Serpengüzel, A. (Institute of Physics Publishing, 1999)
      Photoluminescence (PL) spectra of TlInS2 layered single crystals were investigated in the 500-860 nm wavelength region and in the 11.5-100 K temperature range. We observed two PL bands centred at 515 nm (2.41 eV, A band) ...