Search for: layered-semiconductors
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    Developing seedless growth of atomically thin semiconductor layers: Application to transition metal dichalcogenides

    , Article Ceramics International ; Volume 44, Issue 13 , 2018 , Pages 15795-15803 ; 02728842 (ISSN) Rahmani Taji Boyuk, M. R ; Sovizi, S ; Ghanbari, H ; Simchi, A ; Aboudzadeh, N ; Sharif University of Technology
    Elsevier Ltd  2018
    Controlled growth of atomic monolayers of IV-VII transition metal dichalcogenides (TMDs) has provided unprecedented opportunities to fabricate modern optoelectronic nanodevices. However, synthesis of large-area and high quality two-dimensional TMDs is still challenging. We have synthesized WS2 and MoS2 nanosheets by atmospheric pressure chemical vapor deposition (APCVD) at wide-range of processing conditions. The nanostructures were analyzed by optical and confocal microscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction to determine the thickness, lateral size and structure of the deposits. Through designing and performing of a set of controlled experiments as well as... 

    The role of a vapor-assisted solution process on tailoring the chemical composition and morphology of mixed-halide perovskite solar cells

    , Article CrystEngComm ; Volume 20, Issue 31 , 2018 , Pages 4428-4435 ; 14668033 (ISSN) Tafazoli, S ; Timasi, N ; Nouri, E ; Mohammadi, M. R ; Sharif University of Technology
    Royal Society of Chemistry  2018
    Herein, we report a modified two-step method to construct a uniform and pinhole-free polycrystalline perovskite film with large grains up to the microscale using lead mixed-halide (PbI2-PbCl2) precursor solutions to guarantee the device functioning. Commonly used sequential deposition methods based on dip- and spin-coatings are combined with a vapor-assisted solution process to improve the perovskite morphology and tune the residual lead mixed-halides. These can enhance the optical absorption and efficiency of perovskite solar cell (PSC) devices. The impact of the Cl content in the lead mixed-halide precursors and the employed preparation methods on the photovoltaic performance of PSCs are... 

    Plasmonic enhancement of photocurrent generation in two-dimensional heterostructure of WSe2/MoS2

    , Article Nanotechnology ; Volume 32, Issue 32 , 2021 ; 09574484 (ISSN) Ghods, S ; Esfandiar, A ; Sharif University of Technology
    IOP Publishing Ltd  2021
    Enhancing the photoresponse of single-layered semiconductor materials is a challenge for high-performance photodetectors due to atomically thickness and limited quantum efficiency of these devices. Band engineering in heterostructure of transition metal chalcogenides (TMDs) can sort out part of this challenge. Here, we address this issue by utilizing the plasmonics phenomenon to enrich the optoelectronics property of the WSe2/MoS2 heterojunction and further enhancement of photoresponse. The introduced approach presents a contamination-free, tunable and efficient way to improve light interactions with heterojunction devices. The results showed a 3600-fold enhancement in photoresponsivity and... 

    Photothermal properties of two-dimensional molybdenum disulfide (MoS2) with nanoflower and nanosheet morphology

    , Article Materials Research Bulletin ; Volume 152 , 2022 ; 00255408 (ISSN) Salimi, M ; Shokrgozar, M. A ; Hamid, D. H ; Vossoughi, M ; Sharif University of Technology
    Elsevier Ltd  2022
    PEGylated MoS2 nanoflower (MoS2-NF) and nanosheet (MoS2-NS) are synthesized through a one-pot hydrothermal method as photo absorbing agent (PAA). It is found that employing different thiol precursors result in distinct morphologies. The products are structurally, chemically, and morphologically characterized. Electron microscopy demonstrates the formation of sheet and flower morphologies of MoS2. Fourier transform infrared (FTIR) and thermal gravimetric (TGA) analysis confirm the PEGylation of MoS2 nanostructures. Raman and X-ray photoelectron spectroscopy (XPS) confirm the formation of 1T/2H structure of both samples. MoS2-NS demonstrates higher NIR absorption than MoS2-NF with a mass... 

    Metal-Organic framework derived CuCo2O4 as a promising Co-Catalyst for improving electrochemical hydrogen evolution activity of MoS2 nanoflowers

    , Article Chemical Physics Letters ; Volume 809 , 2022 ; 00092614 (ISSN) Koohdareh, A.R ; Taherinia, D ; Akbarzadeh, E ; Gholami, M.R ; Sharif University of Technology
    Elsevier B.V  2022
    The great promise of electrochemical water splitting for green and sustainable hydrogen fuel production has motivated researchers to strive for more efficient and low-cost catalysts based on non-precious metals. In this study, MoS2 nanoflowers decorated with CuCo2O4 were successfully synthesized, and their catalytic activities toward the electrochemical hydrogen evolution reaction (HER) in an alkaline medium were investigated. The composition, structure, and morphology of the as-synthesized catalysts were explored by various techniques such as FT-IR, XRD, BET, SEM, and TEM. To maximize the catalytic activity, the composition of the nanocomposites was systematically varied. Catalytic results... 

    Resolving a critical instability in perovskite solar cells by designing a scalable and printable carbon based electrode-interface architecture

    , Article Advanced Energy Materials ; Volume 8, Issue 31 , 2018 ; 16146832 (ISSN) Mashhoun, S ; Hou, Y ; Chen, H ; Tajabadi, F ; Taghavinia, N ; Egelhaaf, H. J ; Brabec, C. J ; Sharif University of Technology
    Wiley-VCH Verlag  2018
    Thin-film solar cells based on hybrid organo-halide lead perovskites achieve over 22% power conversion efficiency (PCE). A photovoltaic technology at such high performance is no longer limited by efficiency. Instead, lifetime and reliability become the decisive criteria for commercialization. This requires a standardized and scalable architecture which does fulfill all requirements for larger area solution processing. One of the most highly demanded technologies is a low temperature and printable conductive ink to substitute evaporated metal electrodes for the top contact. Importantly, that electrode technology must have higher environmental stability than, for instance, an evaporated silver... 

    Phase transition and field effect topological quantum transistor made of monolayer MoS2

    , Article Journal of Physics Condensed Matter ; Volume 30, Issue 23 , 2018 , May ; 09538984 (ISSN) Simchi, H ; Simchi, M ; Fardmanesh, M ; Peeters, F. M ; Sharif University of Technology
    Institute of Physics Publishing  2018
    We study topological phase transitions and topological quantum field effect transistor in monolayer molybdenum disulfide (MoS2) using a two-band Hamiltonian model. Without considering the quadratic (q 2) diagonal term in the Hamiltonian, we show that the phase diagram includes quantum anomalous Hall effect, quantum spin Hall effect, and spin quantum anomalous Hall effect regions such that the topological Kirchhoff law is satisfied in the plane. By considering the q 2 diagonal term and including one valley, it is shown that MoS2 has a non-Trivial topology, and the valley Chern number is non-zero for each spin. We show that the wave function is (is not) localized at the edges when the q 2... 

    Two-dimensional materials for gas sensors: from first discovery to future possibilities

    , Article Surface Innovations ; Volume 6, Issue 4-5 , 2018 , Pages 205-230 ; 20506252 (ISSN) Barzegar, M ; Tudu, B ; Sharif University of Technology
    ICE Publishing  2018
    Semiconductor gas sensors have been developed so far on empirical bases, but now recent innovative materials for advancing gas sensor technology have been made available for further developments. Two-dimensional (2D) materials have gained immense attention since the advent of graphene. This attention inspired researchers to explore a new family of potential 2D materials. The superior structural, mechanical, optical and electrical properties of 2D materials made them attractive for next-generation smart device applications. There are considerable improvements and research studies on graphene, molybdenum disulfide (MoS2), tungsten disulfide (WS2), tin sulfide (SnS2), black phosphorus and other... 

    Low-Frequency model for hand-calculations in circuit design with TMDC-based transistors

    , Article IEEE Transactions on Electron Devices ; Volume 66, Issue 11 , 2019 , Pages 5011-5018 ; 00189383 (ISSN) Omdeh Ghiasi, H ; Safarian, A ; Pourfath, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    This article presents an applicable intuitive current-voltage model for long-channel transistors based on 2-D materials. This model carefully predicts the transistor behavior in the saturation and triode regions, which are important for analog and digital applications. Moreover, the effect of mobility degradation on the characteristics of the transistor is probed. As a case study, the developed model has been applied to a transistor with mono-layer MoS2 as the channel material. The excellent agreement with experimental data verifies the accuracy of the model. Finally, the introduced model has been utilized to design an amplifier, a differential pair, and a low-frequency common source mixer... 

    Effect of CsCl additive on the morphological and optoelectronic properties of formamidinium lead iodide perovskite

    , Article Solar RRL ; Volume 3, Issue 11 , 2019 ; 2367198X (ISSN) Chavan, R. D ; Prochowicz, D ; Yadav, P ; Tavakoli, M. M ; Nimbalkar, A ; Bhoite, S. P ; Hong, C. K ; Sharif University of Technology
    Wiley-VCH Verlag  2019
    The quality of perovskite films plays a crucial role in improving the optoelectronic properties and performance of perovskite solar cells (PSCs). Herein, high-quality CsxFA1−xPbI3 perovskite films with different compositions (x = 0, 5, 10, and 15) are achieved by controlling the amount of cesium chloride (CsCl) in the respective FAPbI3 precursor solution. The effects of CsCl addition on the morphological and optoelectronic properties of the resulting perovskite films and on the performance of the corresponding devices are systematically studied. Introduction of CsCl into FAPbI3 shows a great potential to stabilize the α-FAPbI3 perovskite phase by forming CsxFA1−xPbI3 films with improved... 

    First-principles study of molecule adsorption on Ni-decorated monolayer MoS2

    , Article Journal of Computational Electronics ; Volume 18, Issue 3 , 2019 , Pages 826-835 ; 15698025 (ISSN) Barzegar, M ; Berahman, M ; Asgari, R ; Sharif University of Technology
    Springer New York LLC  2019
    The interactions between four different gas molecules (methanol, o-xylene, p-xylene and m-xylene) and Ni-decorated monolayer MoS2 were investigated by means of density functional computations to exploit its potential application as a gas sensor. The electronic properties of the Ni-decorated monolayer MoS2 and gas molecule (adsorbent–adsorbate properties) strongly depend on the Ni-decorated monolayer MoS2 structure and the molecular configuration of the adsorbate. The adsorption properties of volatile organic compound (VOC) molecules on Ni-decorated MoS2 has been studied taking into account the parameters such as adsorption energy, energy bandgap, density of states, and Mulliken charge... 

    On the performance of vertical MoS2 nanoflakes as a gas sensor

    , Article Vacuum ; Volume 167 , 2019 , Pages 90-97 ; 0042207X (ISSN) Barzegar, M ; Iraji zad, A ; Tiwari, A ; Sharif University of Technology
    Elsevier Ltd  2019
    Despite their potential applications, a limited number of studies for synthesizing vertical MoS2 nanoflakes especially via CVD have been reported so far, which generally involve tedious complex- and/or multi-step growth processes. In this study, direct synthesis of vertical MoS2 nanoflakes grown on the SiO2/Si substrate during a rapid sulfidation process by CVD method has been reported. Material characterization was performed using Raman spectroscopy, XRD and FE-SEM. The XRD results indicated the dominant phase of 2H–MoS2 within the synthesized layers. The characteristic distance between the two dominant peaks of E1 2g and A1g in the Raman spectra confirms the multi-layered structure for... 

    Pure sulfide Cu2ZnSnS4 layers through a one-step low-temperature PLD technique: Insight into simulation on modified back contact to overcome the barrier of MoS2

    , Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 262 , 2020 Heidariramsheh, M ; Haghighi, M ; Dabbagh, M. M ; Mahdavi, S. M ; Sharif University of Technology
    Elsevier Ltd  2020
    Targeting on the selenium free, pure sulfide kesterite compound (CZTS) allows retention of the higher band gap nontoxic absorber for a single-junction solar cell. In this work, CZTS thin films were deposited by the PLD method and the Structural/optical properties, as well as Mott–Schottky analysis, were studied at different substrate temperatures. Without undergoing the sulfurization process, the single-phase CZTS thin film is prepared at 300 ℃. In the second step, a numerical simulation is performed using the solar cell capacitance simulator to study the effect of the grading layer of MoS(Se)2 on the rear side of pure sulfide kesterite based solar cells. The device with a MoSe2 coated... 

    Heat transfer hybrid nanofluid (1-Butanol/MoS2–Fe3O4) through a wavy porous cavity and its optimization

    , Article International Journal of Numerical Methods for Heat and Fluid Flow ; 2020 Hosseinzadeh, K ; Montazer, E ; Shafii, M. B ; Ganji, D. D ; Sharif University of Technology
    Emerald Group Holdings Ltd  2020
    Purpose: The purpose of this paper is to investigate natural convection in a porous wavy-walled enclosure that is including a cylinder cavity in the middle of it and filled with a hybrid nanofluid contains 1-Butanol as the base fluid and MoS2–Fe3O4 hybrid nanoparticles. Design/methodology/approach: The domain of interest is bounded by constant temperature horizontal corrugated surfaces and isothermal vertical flat surfaces. The numerical outputs are explained in the type of isotherms, streamline and average Nusselt number with variations of the Rayleigh number, Hartmann number, nanoparticle shape factor and porosity of the porous medium. For solving the governing equations, the finite... 

    Near-room-temperature spin caloritronics in a magnetized and defective zigzag MoS2 nanoribbon

    , Article Journal of Computational Electronics ; Volume 19, Issue 1 , 2020 , Pages 137-146 Zakerian, F ; Fathipour, M ; Faez, R ; Darvish, G ; Sharif University of Technology
    Springer  2020
    Using a tight-binding approach and first-principles calculations combined with the nonequilibrium Green’s function method, the thermal spin transport in a zigzag molybdenum disulfide (MoS 2) nanoribbon in the proximity of a ferromagnetic insulator that induces a local exchange magnetic field in the center of the nanoribbon is investigated. It is found that a pure spin current and perfect spin Seebeck effect with zero charge current can be generated by applying a thermal gradient and local exchange magnetic field without a bias voltage near room temperature. Furthermore, it is shown that this nanoscale device can act as a spin Seebeck diode for the control of thermal and spin information in... 

    Robust water splitting on staggered gap heterojunctions based on WO3∖WS2–MoS2 nanostructures

    , Article Renewable Energy ; Volume 162 , December , 2020 , Pages 504-512 Mojaddami, M ; Simchi, A ; Sharif University of Technology
    Elsevier Ltd  2020
    The high charge carrier recombination rate and weak oxygen evolution kinetics have impeded the efficiency of WO3 photoelectrodes for water splitting. We present a novel type II heterojunction semiconductor based on mixed WS2 and MoS2 nanosheets on WO3 nanoflakes hydrothermally grown on highly porous W skeletons. The chemically exfoliated transition metal dichalcogenide (TMD) sheets with submicrometric lateral sizes were deposited on the surface of WO3 nanoflakes by the electrophoretic technique to fabricate a staggered gap heterojunction. The photoanode exhibited an impressive current density of 14.9 mA cm−2 at 1.23 VRHE which comprised ∼1.7 mA cm−2 photocurrent under 100 mW cm−2 simulated... 

    Green synthesis of ternary carbon dots (CDs)/MIL-88B (Fe)/Bi2S3 nanocomposite via MOF templating as a reusable heterogeneous nanocatalyst and nano-photocatalyst

    , Article Materials Research Bulletin ; Volume 138 , 2021 ; 00255408 (ISSN) Gholizadeh Khasevani, S ; Shahsavari, S ; Gholami, M.R ; Sharif University of Technology
    Elsevier Ltd  2021
    An environmentally friendly heterogeneous ternary carbon dots (CDs)/MIL-88B (Fe)/Bi2S3 nanocomposite was synthesized by a multistep method. In this study, we have studied low-temperature calcination with relatively inexpensive reactants. The sufficient CD arrays were generated by loading the glucose molecules into the pores of an as-obtained metal-organic framework (MOF), i.e. MIL-88B (Fe)), by heating to 200 °C. Fabricated nanocomposite structures were characterized by FT-IR, XRD, EIS, SEM, TEM, BET, and TGA techniques, demonstrating the decoration of the Bi2S3 on the CDs/MIL-88B (Fe) nanocomposite surface. MOF templating has been chosen as a systemic method for limited size CD formation... 

    Solidification enhancement in triplex thermal energy storage system via triplets fins configuration and hybrid nanoparticles

    , Article Journal of Energy Storage ; Volume 34 , 2021 ; 2352152X (ISSN) Hosseinzadeh, K ; Montazer, E ; Shafii, M. B ; Ganji, A. R. D ; Sharif University of Technology
    Elsevier Ltd  2021
    Latent thermal energy storage dependent on Phase Change Materials (PCMs) proposes a possible answer for modifying the availability of alternating energy from renewable sources such as wind and solar. They can possibly store large amounts of energy in moderately tiny dimensions as well as through almost isothermal procedures. Notwithstanding, low thermal conductivity values is a significant disadvantage of the present PCMs which critically restrict their energy storage usage. Likewise, this unacceptably decreases the solidification/melting rates, hence causing the system response time to be excessively lengthy. The present examination accomplished a better PCM solidification rate with a... 

    Low loaded MoS2/Carbon cloth as a highly efficient electrocatalyst for hydrogen evolution reaction

    , Article International Journal of Hydrogen Energy ; 2021 ; 03603199 (ISSN) Shaker, T ; Mehdipour, H ; Moshfegh, A. Z ; Sharif University of Technology
    Elsevier Ltd  2021
    Active edge sites of MoS2 nanosheets exhibit promising futures for hydrogen evolution reaction (HER), comparable with remarkable performances of highly cost platinum. However, 3D structures of MoS2 suffer from a lack of high mobility and unexposed active sites which lower the electrocatalytic activity. In this study, we show that there is a balance between increasing the active sites on the one hand and managing the charge transfer to facilitate the reaction on the other hand, and achieving this balance increases the efficiency of the electrocatalyst tremendously. For this purpose, we directly attached exfoliated MoS2 nanosheets onto carbon cloth (CC) substrate as a 3D network of conductive... 

    Efficient FAPbI3-PbS quantum dot graphene-based phototransistors

    , Article New Journal of Chemistry ; Volume 45, Issue 34 , 2021 , Pages 15285-15293 ; 11440546 (ISSN) Aynehband, S ; Mohammadi, M ; Poushimin, R ; Nunzi, J. M ; Simchi, A ; Sharif University of Technology
    Royal Society of Chemistry  2021
    The high mobility of charge carriers in graphene (G) together with the ease of processing and tunable optical properties of colloidal quantum dots (CQD) has provided high-performance hybrids for the next generation of phototransistors. In order to get a higher quality film of PbS QDs, understanding the effect of the ligand exchange method is critical. So, to improve the interdot electronic coupling, we propose a new conducting ligand to prepare a dense and self-assembled active layer of FAPbI3-PbS quantum dots on G/Si/SiO2substrates. Quantum dot (QD) nanocrystalline films were preparedviatwo different procedures: liquid phase ligand exchange (LPE) and solid phase ligand exchange (SPE). SPE...