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semiconductor-quantum-wells
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Enhancement of Mn luminescence in ZnS:Mn multi-quantum-well structures
, Article Applied Physics Letters ; Volume 83, Issue 22 , 2003 , Pages 4616-4618 ; 00036951 (ISSN) ; Makino, H ; Yao, T ; Sharif University of Technology
2003
Abstract
The efficiency of Mn luminescence is enhanced in low-thickness ZnS:Mn layers. While various hypotheses can be considered to explain the phenomenon, it seems more reasonable to consider the luminescence enhancement effect a result of the formation of dot-like regions with higher local Mn concentration
Analysis of carrier dynamic effects in transistor lasers
, Article Optical Engineering ; Volume 51, Issue 2 , December , 2012 ; 00913286 (ISSN) ; Mirmoeini, S. Z ; Faez, R ; Sharif University of Technology
2012
Abstract
We present an analytical model to analyze the influence of carrier dynamics on the static and dynamic responses of transistor laser (TL). Our analysis is based on solving the continuity equation and the rate equations which incorporate the virtual states as a conversion mechanism. We show that the details of the dc and small signal behavior of transistor lasers are strongly affected by the escape and capture times of carriers in quantum well (QW). Also, the effects of carrier recombination lifetime in the quantum well and base regions on the TL static and dynamic performances are investigated
Large signal analysis of double quantum well transistor laser
, Article Optical and Quantum Electronics ; Volume 45, Issue 5 , 2013 , Pages 389-399 ; 03068919 (ISSN) ; Faez, R ; Sharif University of Technology
2013
Abstract
In this paper, we present an analytical model for the large-signal analysis of the double quantum well (DQW) transistor laser. Our model is based on solving the continuity equation and the rate equations which incorporate the virtual states as a conversion mechanism. By using the presented model, effects of barrier width on DQW transistor laser static and dynamic performances are investigated. Also the static and dynamic responses of DQW transistor lasers are compared with single quantum well ones. Simulation results are in agreement with the numerical and experimental results reported by other researchers
Generation of two-soliton and three-soliton molecules in a circular fiber array laser
, Article Laser Physics ; Volume 28, Issue 4 , March , 2018 ; 1054660X (ISSN) ; Rooholamininejad, H ; Bahrampour, A ; Sharif University of Technology
Institute of Physics Publishing
2018
Abstract
In this work, the generation of two-soliton and three-soliton molecules in a circular fiber array laser with an active optical central fiber is studied. Certain fibers of the array are excited by Gaussian and super-Gaussian pulses. The central fiber of the circular fiber laser is a rare-earth doped fiber. A circular fiber array is employed as a saturable absorber in a soliton mode locked fiber laser. Generation of two-soliton and three-soliton molecules are observed in our simulation. Numerical calculation of binding energy shows that the super-Gaussian pulse tends to be more stable, and therefore it would be a proper choice for the generation of soliton molecules in the circular fiber array...
CdS nanoparticle sensitized titanium dioxide decorated graphene for enhancing visible light induced photoanode
, Article Applied Surface Science ; Vol. 320, issue , 30 November , 2014 , pp. 772-779 ; ISSN: 01694332 ; Faraji, M ; Nien, Y. T ; Moshfegh, A. Z ; Sharif University of Technology
Abstract
CdS/TiO2/graphene (CTG) nanocomposite thin films were synthesized by a facile production route. The TiO2/graphene (TG) nanocomposite was initially fabricated by sol-gel method in such a way that TiO2 nanoparticles loaded on graphene oxide (GO) sheet via photocatalytic process. Then, CdS nanoparticles were deposited on the TG thin film by successive ion layer adsorption and reaction process (SILAR) approach. Based on atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, the TG thin film possessed a larger surface area as compared with the pure TiO2 thin film due to presence of graphene sheet. UV/visible spectroscopy exhibited...
Optical modulation by conducting interfaces
, Article IEEE Journal of Quantum Electronics ; Volume 49, Issue 7 , 2013 , Pages 607-616 ; 00189197 (ISSN) ; Khorasani, S. A ; Sharif University of Technology
2013
Abstract
We analyze the interaction of a propagating guided electromagnetic wave with a quantum well embedded in a dielectric slab waveguide. First, we design a quantum well based on InAlGaAs compounds with the transition energy of 0.8 eV corresponding to a wavelength of 1.55 μm. By exploiting the envelope function approximation, we derive the eigenstates of electrons and holes and the transition dipole moments. Next, we calculate the electrical susceptibility of a three-level quantum system (as a model for the 2-D electron gas trapped in the waveguide), by using phenomenological optical Bloch equations. We show that the 2-D electron gas behaves as a conducting interface, whose conductivity can be...
Detemining the thickness of barriers and well of Resonance Tunneling Diodes by specified I-V characteristic
, Article Applied Mechanics and Materials ; Volume 110-116 , 2012 , Pages 5464-5470 ; 16609336 (ISSN) ; 9783037852620 (ISBN) ; Ghorbanalipour, S ; Faez, R ; Sharif University of Technology
Abstract
In this paper, a method of determining physical dimension of Double Barrier Quantum Well (DBQW) of Resonance Tunneling Diodes (RTDs) is presented by using I-V characteristic governing on them. In this procedure, first we have used performance metrics related to RTDs I-V characteristic such as Peak to Valley Current Ratio (PVCR), peak current density (JP), valley current density (JV) and Voltage Swing (VS), and by some other arbitrary points, we have fitted a curve to the RTD current-voltage equation by MATLAB software. Then we have obtained the physical parameter of I-V equation and adjusted some of them with modification coefficients. Next, by choosing the material of barriers and the well...
A novel thermo-photovoltaic cell with quantum-well for high open circuit voltage
, Article Superlattices and Microstructures ; Volume 83 , July , 2015 , Pages 61-70 ; 07496036 (ISSN) ; Faez, R ; Akbari Eshkalak, M ; Sharif University of Technology
Academic Press
2015
Abstract
Abstract We design a thermo-photovoltaic Tandem cell which produces high open circuit voltage (Voc) that causes to increase efficiency (η). The currently used materials (AlAsSb-InGaSb/InAsSb) have thermo-photovoltaic (TPV) property which can be a p-n junction of a solar cell, but they have low bandgap energy which is the reason for lower open circuit voltage. In this paper, in the bottom cell of the Tandem, there is 30 quantum wells which increase absorption coefficients and quantum efficiency (QE) that causes to increase current. By increasing the current of the bottom cell, the top cell thickness must be increased because the top cell and the bottom cell should have the same current. In...
Spray pyrolysis deposition of ZnFe2O4/Fe2O3 composite thin films on hierarchical 3-D nanospikes for efficient photoelectrochemical oxidation of water
, Article Journal of Physical Chemistry C ; Volume 121, Issue 34 , 2017 , Pages 18360-18368 ; 19327447 (ISSN) ; Hussain, S ; Waleed, A ; Tavakoli, M. M ; Yang, S ; Khawar Rauf, M ; Fan, Z ; Arif Nadeem, M ; Sharif University of Technology
Abstract
In this work, we study the role of nanotextured ZnFe2O4/Fe2O3composite thin films fabricated by ultrasonic spray pyrolysis (USP) on the photoelectrochemical water oxidation reactions. The ZnFe2O4/Fe2O3 composites with different molar ratios are deposited on three-dimensional nanospikes (NSP) substrate, and the results are compared with those for planar devices. It is observed that optical absorption and charge separation due to larger surface area is significantly enhanced in nanotextured photoactive ZnFe2O4/Fe2O3 films. After characterization of ZnFe2O4/Fe2O3 composite films with different molar ratios (ZF1, ZF2, and ZF3), we find that the nanotextured ZF1 composite with a molar ratio of...
Investigating optical properties of one-dimensional photonic crystals containing semiconductor quantum wells
, Article International Journal of Optics ; Volume 2017 , 2017 ; 16879384 (ISSN) ; Asgari, M ; Sabatyan, A ; Sharif University of Technology
Abstract
This study examined MQWs made of InGaAs/GaAs, InAlAs/InP, and InGaAs/InP in terms of their band structure and reflectivity. We also demonstrated that the reflectivity of MQWs under normal incident was at maximum, while both using a strong pump and changing incident angle reduced it. Reflectivity of the structure for a weak probe pulse depends on polarization, intensity of the pump pulse, and delay between the probe pulse and the pump pulse. So this system can be used as an ultrafast all-optical switch which is inspected by the transfer matrix method. After studying the band structure of the one-dimensional photonic crystal, the optical stark effect (OSE) was considered on it. Due to the OSE...
Photoelectrochemical activity of graphene quantum dots/hierarchical porous TiO2 photoanode
, Article Journal of Alloys and Compounds ; Volume 721 , 2017 , Pages 36-44 ; 09258388 (ISSN) ; Safa, S ; Ebrahimi, M ; Yousefzadeh, S ; Moshfegh, A. Z ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In this study, initially graphene quantum dots (GQDs) were synthesized by an electrochemical technique and hierarchical porous TiO2 were made by a sol – gel method. Subsequently, GQDs/hierarchical porous TiO2 nanocomposites were prepared by two different methods for the purpose of comparison: spin coating (SC) and electrophoretic (EP) deposition. The GQDs/hierarchical porous TiO2 nanocomposites were characterized by various analytical methods including field emission scanning electron microscopy, atomic force microscopy, transmission electron microscopy, high resolution transmission electron microscopy, Fourier transform infra-red spectroscopy, photoluminescence spectroscopy and...
Quantum well design and diffraction efficiency of quantum well light emitting diode
, Article Photonic and Phononic Crystal Materials and Devices IX, San Jose, CA, 27 January 2009 through 29 January 2009 ; Volume 7223 , 2009 ; 0277786X (ISSN) ; Eftekharian, A ; Sodagar, M ; Khorasani, S ; Adibi, A ; Sharif University of Technology
2009
Abstract
In this work, a GaN-based quantum well LED is theoretically analyzed in a multi-layer structure composed of a quantum well embedded in a waveguide core surrounded by photonic crystal slab and a sapphire substrate. The electromagnetic eigenmodes are obtained throughout above structure via revised plane wave-scattering matrix method. The omnidirectional transmission and reflection are investigated for both TE and TM polarizations from diffraction channels in Ewald construction. Then, we introduced angular power density and calculated radiative modes extraction efficiency. All structural parameters, such as lattice geometry, lattice constant, photonic crystal thickness and filling factor, are...
Engineered nanopores-based armchair graphene nanoribbon fet with resonant tunneling performance
, Article IEEE Transactions on Electron Devices ; Volume 66, Issue 12 , 2019 , Pages 5339-5346 ; 00189383 (ISSN) ; Ahmadi, V ; Faez, R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
This article presents a novel armchair graphene nanoribbon (AGNR) field-effect transistor with engineered nanopores for resonant tunneling. Two rectangular nanopores are punched to create two potential barriers and one quantum well. Channel and source and drain contacts are AGNR, indicating structure homogeneity. Nonequilibrium Green's function and Poisson's equations are used for structural analysis. The input variables are well width (WW), drain voltage (VD), and barrier width (BW). The effects of repositioning nanopores and AGNR type (i.e., semiconductor and semimetal) are also studied. The impact of the parameters on the density of states, transmission probabilities, peak current (IP)...
When photoluminescence, electroluminescence, and open-circuit voltage diverge-light soaking and halide segregation in perovskite solar cells
, Article Journal of Materials Chemistry A ; Volume 9, Issue 24 , 2021 , Pages 13967-13978 ; 20507488 (ISSN) ; Yang, B ; Kim, Y ; Mohammadpour, R ; Taghavinia, N ; Hagfeldt, A ; Tress, W ; Sharif University of Technology
Royal Society of Chemistry
2021
Abstract
Perovskite solar cells suffer from various instabilities on all time scales. Some of them are driven by light, in particular when employing compounds with mixed halides. Such light soaking effects have been observed to result in performance changes of solar-cell devices. They have also been spectroscopically investigated in detail on films, where the formation of a low-gap iodine-rich phase, seen as a red shift of the PL, has been found to be responsible for a reduced open-circuit voltage. However, studies synchronously examining device performance and its relation to spectroscopy data are scarce. Here, we perform an in operando study, where we investigate the changes of open-circuit voltage...
CuO and ZnO co-anchored on g-C3N4 nanosheets as an affordable double Z-scheme nanocomposite for photocatalytic decontamination of amoxicillin
, Article Applied Catalysis B: Environmental ; Volume 285 , 2021 ; 09263373 (ISSN) ; Hasanvandian, F ; Isari, A. A ; Hayati, F ; Kakavandi, B ; Setayesh, S. R ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In this study, both CuO nanoparticles and ZnO nanorods were anchored on thermally-exfoliated g-C3N4 nanosheets (denoted as CZ@T-GCN) via isoelectric point-mediated annealing process as a novel nano-photocatalyst towards degradation of amoxicillin (AMOX). The features of prepared materials were characterized using BET, UV–vis DRS, XRD, FT-IR, XPS, FE-SEM, TEM, EIS and transient photocurrent techniques. These analyses demonstrated the successful formation of heterojunctions between components of CZ@T-GCN nanocomposite, which reflected in significantly increased electron-hole separation and enhanced degradation of AMOX as compared with pure substances. The investigation of influential operative...
Stable Photodetectors based on fstable photodetectors based on formamidinium lead iodide quantum well perovskite nanoparticles fabricated with excess organic cations.ormamidinium lead iodide quantum well perovskite nanoparticles fabricated with excess organic cations
, Article ACS Applied Nano Materials ; Volume 4, Issue 8 , 2021 , Pages 7788-7799 ; 25740970 (ISSN) ; Mohammadi, M ; Rezaei, N.T ; Aynehband, S ; Shooshtari, L ; Mohammadpour, R ; Simchi, A ; Sharif University of Technology
American Chemical Society
2021
Abstract
Metal halide perovskite nanoparticles have recently attracted immense interest for photodetectors due to their outstanding optical and electronic properties such as high carrier diffusion length, tunable band gap (light absorption range), and high photoluminescence (PL) efficiency. Although significant progress has been achieved in the development of perovskites, their stability is yet to be addressed. To improve the stability and quantum efficiency of FAPbI3 perovskite nanocrystals, we present a room temperature protocol to fabricate fully passivated and stable FAPbI3 nanocrystals via 2D growth in the presence of amine ligands and an excess amount of the organic cations. The crystallization...
Tuning composition of electrospun ZnO/CuO nanofibers: toward controllable and efficient solar photocatalytic degradation of organic pollutants
, Article Journal of Physical Chemistry C ; Volume 121, Issue 6 , 2017 , Pages 3327-3338 ; 19327447 (ISSN) ; Samadi, M ; Mahmoodi, N. M ; Pourjavadi, A ; Mehdipour, H ; Moshfegh, A. Z ; Sharif University of Technology
American Chemical Society
2017
Abstract
ZnO/CuO nanofibers, with different CuO concentrations, were fabricated by one-step electrospinning of the polymer precursor and annealing in air. Scanning electron microscopy (SEM) showed smooth and beadless morphology for the synthesized nanofibers, while X-ray diffraction (XRD) analysis revealed formation of hexagonal and monoclinic crystalline structure phases for ZnO and CuO nanofibers, respectively. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of CuO on the surface of ZnO nanofibers. For further confirming the formation of chemical bonds, Fourier transform infrared (FT-IR) spectroscopy was employed. The effect of Cu contents in the overall electronic band...
The highly crystalline tellurium doped ZnO nanowires photodetector
, Article Journal of Crystal Growth ; Volume 522 , 2019 , Pages 214-220 ; 00220248 (ISSN) ; Teimouri, M ; Jafari Marandi, S ; Shariati, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
In this paper, the stable and reproducible tellurium doped ZnO nanowires (Te-ZnO NWs) photodetector with intensive responsively is presented. The Te-ZnO NWs were fabricated by physical vapor deposition (PVD) growth mechanism. Field emission scanning electron microscope (FESEM) images showed that the fabricated nanowires were 50 nm in diameter and several microns in length. The high resolution transmission electron microscopy indicated that the synthesized nanowires were crystalline and their phase characterization was validated by the X-ray diffraction (XRD). The photoluminescence (PL) studies of these nanowires showed a strong photoluminescence (PL) emission peak in the green region. It was...
Combustion synthesis of g-C3N4/Fe2O3 nanocomposite for superior photoelectrochemical catalytic performance
, Article Applied Surface Science ; Volume 534 , 2020 ; Sadrnezhaad, S. K ; Hosseini H., S. M ; Sharif University of Technology
Elsevier B.V
2020
Abstract
The g-C3N4/Fe2O3 nanocomposite was produced by the solution combustion synthesis (SCS) of iron-nitrate/g-C3N4 mixtures of varying concentration ratios and using urea as a fuel. The following methods did characterization of the products: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller investigation (BET), ultraviolet–visible light analysis (UV–vis) and photoluminescence measurement (PL). Effect of iron nitrate on stability and photocurrent density under simulated visible-light irradiation was determined. The...
Design of a GaN white light-emitting diode through envelope function analysis
, Article IEEE Journal of Quantum Electronics ; Volume 46, Issue 2 , 2010 , Pages 228-237 ; 00189197 (ISSN) ; Sodagar, M ; Eftekharian, A ; Khorasani, S ; Sharif University of Technology
Abstract
In this paper, we present an envelope function analysis technique for the design of the emission spectra of a white quantum-well light-emitting diode (QWLED). The nano- metric heterostructure that we are dealing with is a multiple QW, consisting of periods of three single QWs with various well thicknesses. With the aid of 6 × 6 Luttinger Hamiltonian, we employ the combination of two methods, k · p perturbation and the transfer matrix method, to acquire the electron and hole wave functions numerically. The envelope function approximation was considered to obtain these wave functions for a special basis set. While adjacent valence sub-bands have been determined approximately, the conduction...