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Optoelectronical Nanostructures - Volume:4 Issue: 1, Winter 2019

Journal of Optoelectronical Nanostructures
Volume:4 Issue: 1, Winter 2019

  • تاریخ انتشار: 1397/10/11
  • تعداد عناوین: 7
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  • Zahra Danesh Kaftroudi * Pages 1-25
    To enhance lasers’ power and improve their performance, a model wasapplied for the waveguide design of 400 nm InGaN/InGaN semiconductor laser, whichis much easier to implement. The conventional and new laser structures weretheoretically investigated using simulation software PICS3D, which self-consistentlycombines 3D simulation of carrier transport, self-heating, and optical waveguiding.Excellent agreement between simulation and experimental results was obtained bycareful adjustment of the material parameter in the physical model. Numericalsimulation results demonstrate that the new waveguide structure can efficiently increasethe output power, lower the threshold current, and improve the slope efficiency, whichis simply applicable to any kind of InGaN edge emitting lasers. Flatten band gap in thep-side of the InGaN laser diode in new laser structure resulted in an increase in the holecurrent density in the quantum well while simultaneously the electron confinement inthe active region was effectively created, leading to the increased stimulatedrecombination rate. Furthermore, optical mode-overlap with heavily p-doped wasdeclined, which is the main reason for a better performance of InGaN laser diode.
    Keywords: InGaN Laser Diode, Waveguide Design, Numerical Analysis, PICS3D
  • Ebrahim Heidari * Pages 27-37
    We have studied the formation of relativistic solitary waves due to nonlinearinteraction of strong electromagnetic wave with the plasma wave. Here, our plasma isrelativistic both in temperature and in streaming speed. A set of equations consisting ofscalar and vector potentials together with a third order equation for the enthalpy inphoton gas plasma is obtained analytically. Solutions with single-humped for the scalarpotential and single and double-humped for the vector potential profiles are illustratednumerically. It is shown that the drifting velocity of moving solitons and plasma fluidvelocity both play an important role in the formation of the solutions. The results showthat the amplitude of the potentials increases for higher values of the plasmatemperatures for the region that the flow velocity of the plasma is larger than the solitarywave velocity. For the region with larger amount of the soliton's velocity, the resultsshow opposite behavior. It is also found that in the region where the plasma fluidvelocity exceeds the soliton drifting velocity, all the solutions are excited at highertemperatures relative to the other area.
    Keywords: Nonlinear phenomena, Photon Gas Plasma, Radiation, Relativistic Solitons
  • Reza Pourtajabadi, Maryam Nayeri * Pages 39-49
    The quantum-dot cellular automata (QCA) is considered as an alternative tocomplementary metal oxide semiconductor (CMOS) technology based on physicalphenomena like Coulomb interaction to overcome the physical limitations of thistechnology. The decoder is one of the important components in digital circuits, whichcan be used in more comprehensive circuits such as full adders and memories. Thispaper proposes the 2:4 decoder using multilayer QCA technology. The multilayerdecoder provides requirements of high-density devices with good computing power.The proposed 2:4 active high decoder reduces the clock phases to three, making thecircuit faster than previous ones. Moreover, the number of cells and occupied space aresignificantly reduced, thus reducing power consumption. Multi-layer architecture hasmore reliability than coplanar architecture and allows for the easy layout change. Thestructure was simulated using QCA Designer software, and the simplified expressionsand standard functions have been presented. The simulation results can be useful forusing them in logic circuits.
    Keywords: Quantum-Dot Cellular Automata, Nano Electronics, Majority Voter Gate, Active High Decoder
  • Kazem Pourchitsaz, Mohammad Reza Shayesteh * Pages 51-65
    We present the design and simulation of a single-walled carbon nanotube(SWCNT)-based field-effect transistor (FET) using Silvaco TCAD. In this paper, theself-heating effect modeling of the CNT MOSFET structure is performed and comparedwith conventional MOSFET structure having same channel length. The numericalresults are presented to show the self-heating effect on the I–V characteristics of theCNT MOSFET and conventional MOSFET structures. Results from numericalsimulation show that the maximum temperature rise and the performance degradation ofthe CNT MOSFET are quite lower than that of the conventional MOSFET counterpart.These advantages are contributed by the good electrical and thermal properties of theSWCNTs. Therefore, SWCNT materials have a high capability for the development ofactive devices with low power dissipation and good reliability at high operatingtemperature.
    Keywords: Field Effect Transistor (FET), Single-Walled Carbon Nanotube (SWCNT), Self-Heating Effect, Transistor Characteristic, Threshold Voltage
  • Tahmineh Jalali *, Abdolrasoul Gharaati, Mohammad Rastegar, Mohammad Ghanaatian Pages 67-86
    We studied magnetophotonic crystals (MPCs) with introduced magneticdefect layer sandwiched between magnetic and dielectric Bragg mirrors. Thesemagnetophotonic crystals have excellent capabilities to enhance reflection and Kerrrotation simultaneously. By adjusting spatial configuration such as repetition numbersof Bragg mirrors and thickness of magnetic defect layer, we achieved the Kerr rotationangles more than 75˚ and reflection very close to 1. We briefly described theformulation of finite element method (FEM) and transfer matrix method (TMM). Theelectric field distribution and magnitude of it along the MPCs are simulated using FEM.Using the TMM, we calculated the MO responses of MPCs. With light localizationinside the magnetic defect layer and multiple reflections in it, the magneto-optical (MO)responses of these MPCs were significantly increased. The studied structures in thisresearch have high MO responses that make it suitable for designing MO elements inhighly sensitive devices and optical telecommunication tools.
    Keywords: Magneto-Optics, Magnetophotonic Crystals, Reflectance, Kerr Rotation, Defect Layer
  • Zahra Dehghani Tafti, Mahmood Borhani Zarandi *, Hojjat Amrollahi Bioki Pages 87-97
    Thin films of tin sulfide/cadmium sulfide (SnS/CdS) were prepared bythermal evaporation method at room temperature on a glass substrate and then annealedat different temperature with the aim of optimizing the optical properties of the materialfor use in photovoltaic solar cell devices. The effect of annealing on optical propertiesof SnS/CdS film was studied in the temperature range of 100 to 400 °C with steps of100 °C. The films were characterized by optical absorption spectra. The opticalconstants such as band gap, refractive index (n) and extinction coefficient (k) werecalculated on different annealing temperature and in the wavelength range of 250 nm to750 nm. Analysis of the optical absorption coefficient demonstrated the presence ofdirect optical transition and the corresponding band gap values showed enhancement asdeposition annealing temperature increased. The energy band gap in the range 2.20 eV –3.18 eV has been obtained for a film as-deposited which increases clearly withincreasing annealing temperature. The refractive index and extinction coefficient bothdecrease notably with increasing annealing temperature.
    Keywords: CdS, Optical Properties, SnS, Thermal Annealing, Thin Film, Vacuum Evaporation
  • Nima Karachi *, Masoomeh Emadi, Mojtaba Servatkhah Pages 99-124
    The interaction between nucleotides and carbon nanotubes (CNTs) is a subjectof many investigations for treating diseases but there are many questions in this field thatremain unanswered. Because of experimental methods involve assumptions andinterpretation besides limitations, there are many problems that the best study for them isusing theoretical study. Consequently, theoretical methods have become a competitivealternative to experiments for biochemical investigations. In order to search about theresponse of SWCNTs in binding to DNA, the interaction between 3 different sequencesof B-form single-strand DNA (ssDNA) and outer surface of single-walled carbonnanotubes (SWCNTs) is considered. So we studied the interaction between (5`-ATC-3`,5`-TCA-3`,5`-TCG-3`) and SWCNT by using Molecular Mechanic(MM) ,Hartree-Fock(HF) and Density Functional Theory(DFT,B3LYP) methods in gas phase. The basissets used were STO-3G, 6–31G.In current interest, energy, dipole moment, total atomiccharges and NMR parameters calculated to obtain information about the molecularstructures and stability of these combinations. Our results revealed the effect of DNA baseand the sequence of nucleotides on the interaction of DNA/SWCNTs systems. So, we canpredict that diseases with special mutation are the better aim for Gene therapy. Therefore,the outcome reported in this paper indicates that theoretical data can give us essentialinsights into the nature of molecular structures interacted to nanotubes.
    Keywords: Single Walled Carbon Nanotube (SWCNT)_Density Functional Theory (DFT)_Hartree-Fock ( HF)