فهرست مطالب

Optoelectronical Nanostructures - Volume:4 Issue:2, 2019
  • Volume:4 Issue:2, 2019
  • تاریخ انتشار: 1398/02/11
  • تعداد عناوین: 7
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  • Mohsen Cheraghizade * Pages 1-12
    In this study, lead sulfide (PbS) films were grown on Fluorine-doped TinOxide (FTO) glass substrate by thermal evaporation in a horizontal furnace toinvestigate carrier gas effect on structural, morphological, elemental, optical, electricaland photovoltaic properties of PbS. X-ray diffraction (XRD) patterns confirmed theformation of cubic polycrystalline PbS particles for all samples. The results showed thatusing Ar+H2 as a carrier gas increased crystallite size of the film. Field emissionscanning electron microscopy (FESEM) images showed nano-dimension surfacemorphologies and revealed that using carrier gas can make the obtained films and theirsurface porosities more uniform and regular. Also, the elemental analysis demonstratesthat using mixed carrier gas provides a better stoichiometry for PbS film. Optical andelectrical evaluations indicated improvements in absorption intensity and electricalconductivity of the PbS film when using the mixed carrier gas. Finally, the depositedfilms were characterized as solar cells and their quality parameters (QP) were extractedand presented. The obtained results illustrate the improvement in QPs of PbS solar cellwhen using mixed carrier gas.
    Keywords: Lead sulfide (PbS), Thermal evaporation, Carrier gas, Optoelectronic properties, solar cell
  • Mahsa Roohy, Reza Hosseini * Pages 13-28
    In this paper, we have presented a heterojunction gate all around nanowiretunneling field effect transistor (GAA NW TFET) and have explained its characteristicsin details. The proposed device has been structured using Germanium for source regionand Silicon for channel and drain regions. Kane's band-to-band tunneling model hasbeen used to account for the amount of band-to-band tunneling generation rate per unitvolume of carriers which tunnel from valence band of source region to conduction bandof channel. The simulations have been carried out by three dimensional Silvaco Atlassimulator. Using extensive device simulations, we compared the results of presentedheterojunction structure with those of Silicon gate all around nanowire TFET. Whereasdue to thinner tunneling barrier at the source-channel junction which leads to theincrease of carrier tunneling rate, the heterojunction gate all around nanowire TFETshows excellent characteristics with high on-state current, superior transconductanceand high cut-off frequency.
    Keywords: Heterojunction GAA NW TFET, Silicon GAA NW TFET, On-State, Off-State, Cut-Off Frequency
  • Morteza Mansuri, Ali Mir, Ali Farmani * Pages 29-44
    In the present paper, a nanostructure plasmonic gas sensor based on ringresonator structure at the wavelength range of 0.6-0.9 μm is presented. The plasmonicmaterials/SiO2 with the advantage of high mobility and low loss is utilized as a substratefor structure to obtain some appropriate characteristics for the sensing Performanceparameters. To evaluate the proposed sensor and calculation of performance parametersincluding figure of merit and sensitivity, the effect of the different gas including CarbonDioxide (CO2), Acetonitrile (C2H3N), Carbon disulfide, and Sarin are considered. Forthis purpose 3D-FDTD method is considered. Our calculations show that by couplingbetween the incident waves and the surface plasmons of the structure, a hightransmission ratio of 0.8 and relatively low insertion loss of 6 dB around the wavelengthinterval of 0.6-0.9 μm are achievable. Furthermore, the calculated sensitivity and figureof merit are 28 and 8.75, respectively. This provides a path for development of nanoscalepractical on-chip applications such as plasmonic memory devices.
    Keywords: Plasmonic, Gas sensor, Nanostructure
  • Abdorreza Asrar *, Mojtaba Servatkhah, Mohammad Javad Salehi Pages 45-52
    Optically pumped helium magnetometers are important instruments whichhave many applications in military, mass spectroscopy and space applications. In thispaper, the working principles of helium magnetometers have been explained. There isalso an introduction of a new method for finding the resonant frequency, which hasadvantages to the typical method such as more sample rate possibility and realizing withcheaper prices.
    Keywords: Optically Pumped Magnetometer, Helium Magnetometer, Conic Method
  • Vahid Fallahi, Mahmood Seifouri * Pages 53-68
    In this paper, Using a 2D photonic crystal and a novel square ring resonator,several compact and simple structures have been introduced in the present paper toconstruct optical add/drop filters and multi-channel filter. The difference structures hasbeen designed and simulated by using the proposed square ring resonator and differentdropping waveguides. To do analyses, the finite-difference time-domain method and theplane wave expansion have been used. The three add/drop filters can separate thewavelength of 1554 nm with a transmission coefficient of 100 %, quality factor of 1295and bandwidth of 1.2 nm. The models of structures are simulated by the RSOFT CADLayoutsoftware. The results, flexibility and simplicity of structures have caused fromtheir used to designing of an optical multi-channel filter with a channel spacing of 1.5nm. The advantages of this design include the channel spacing, quality factor,transmission coefficient and bandwidth which are suitable for applicability in opticalcommunication systems such as wavelength division multiplexing systems.
    Keywords: Photonic Crystal, Add, Drop Filter, Photonic Band Gap, Ring Resonator, PWE, FDTD
  • Hamdollah Salehi *, Firoozeh Anis Hoseini Pages 69-82
    In this paper, the structural parameters, energy bands structure, density ofstates and charge density of HgSe in the Zincblende(B3) phase have been investigated.The calculations have been performed using the Pseudopotential method in theframework of density functional theory (DFT) by Quantum Espresso package. Theresults for the electronic density of states (DOS) show that the band gap for HgSe iszero. The obtained energy bands structure for HgSe show that the lowest conductionband minimum and the top of the valence band are degenerate at the center of Brillouinzone (Г),and this compound is a zero-gap material or semimetal. Calculation of electroncharge density in zincblende phase in (110) plane show that this compound has ionicand covalent bond simultaneously. The theoretical calculated optical properties andenergy Loss (EEL) spectrum yield a static refractive index of4.37and a plasmon energyof 22.83eV for cubic phase. This calculation are in good agreement with the othertheoretical and experimental values.
    Keywords: Energy Bands Structure, Mercury Selenide, Pseudopotential, Quantum Espresso. Density Functional Theory
  • Yagub Sefidgar, Hassan Rasooli Saghai *, Hamed Ghatei Khiabani Azar Pages 83-102
    Multi-junction solar cells play a crucial role in the ConcentratedPhotovoltaic (CPV) Systems. Recent developments in CPV concerning high powerproduction and cost effective-ness along with better efficiency are due to theadvancements in multi-junction cells. This paper presents a simulation model of thegeneralized Multi-junction solar cell and introduces a two-bond solar cell based onInGaP/GaAs with an AlGaAs/GaAs tunnel layer.For enhancing the efficiency of theproposed solar cell, the model adopts absorption enhancement techniques as well asreducing loss of recombination by manipulating number of junctions and varying thematerial properties of the multi-junctions and the tunneling layer. The proposed Multijunctionsolar cell model employing tunnel junctions can improve efficiency up to by35.6%. The primary results of the simulation for the proposed structure indicate that it ispossible to reduce the loss of recombination by developing appropriate lattice matchamong the layers; it is also likely to have suitable absorption level of the phonons.Simulation results presented in this paper are in agreement with experimental results.
    Keywords: Two-Bond Solar Cell, Tunnel Layer, Lattice Matching, Recombination