Search for: thin-films
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    Simulation of imaging in tapping-mode atomic-force microscopy: a comparison amongst a variety of approaches

    , Article Journal of Physics D: Applied Phyics ; Vol.44, Number 7, p.1-9, 2011 Nejat Pishkenari, H ; Mahboobi, S. H ; Meghdari, A. (Ali) ; Sharif University of Technology
    Models capable of accurate simulation of microcantilever dynamics coupled with complex tip–sample interactions are essential for interpretation and prediction of the imaging results in amplitude modulation or tapping-mode atomic-force microscopy (AM-AFM or TM-AFM). In this paper, four approaches based on combinations of lumped and finite element methods for modelling of cantilever dynamics, and van der Waals and molecular dynamics for modelling of tip–sample interactions, are used to simulate the precise imaging by AM-AFM. Based on the simulated imaging and force determination, the efficiency of different modelling schemes is evaluated. This comparison is performed considering their... 

    The effect of annealing temperature on the statistical properties of WO3 surface

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Issue 9 , 2006 ; 17425468 (ISSN) Jafari, G. R ; Saberi, A. A ; Azimirad, R ; Moshfegh, A. Z ; Rouhani, S ; Sharif University of Technology
    We have studied the effect of annealing temperature on the statistical properties of WO3 surface using atomic force microscopy (AFM) techniques. We have applied both level crossing and structure function methods. Level crossing analysis indicates an optimum annealing temperature of around 400°C at which the effective area of the WO3 thin film is maximum, whereas the composition of the surface remains stoichiometric. The complexity of the height fluctuation of surfaces was characterized by roughness, the roughness exponent and the lateral size of surface features. We have found that there is a phase transition at around 400°C from one set to two sets of roughness parameters. This happens due... 

    Sintering characterizations of Ag-nano film on silicon substrate

    , Article Advanced Materials Research ; Volume 829 , 2014 , Pages 342-346 ; ISSN: 10226680 ; ISBN: 9783037859070 Keikhaie, M ; Akbari, J ; Movahhedi, M. R ; Alemohammad, H ; Sharif University of Technology
    Nowadays, thin films have many applications in every field. So, in order to improve the performance of thin film devices, it is necessary to characterize their mechanical as well as electrical properties. In this research work we focus on the development of a model for the analysis of the mechanical and electrical properties of silver nanoparticles deposited on silicon substrates. The model consists of inter-particle diffusion modeling and finite element analysis. In this study, through the simulation of the sintering process, it is shown that how the geometry, density, and electrical resistance of the thin film layer are changed with sintering conditions. The model is also used to... 

    Nanodiamond Decorated with Silver Nanoparticles as a Sensitive Film Modifier in a Jeweled Electrochemical Sensor: Application to Voltammetric Determination of Thioridazine

    , Article Electroanalysis ; Volume 25, Issue 2 , 2013 , Pages 417-425 ; 10400397 (ISSN) Shahrokhian, S ; Hosseini Nassab, N ; Sharif University of Technology
    Nanodiamond-graphite (NDG) decorated with Ag nanoparticles (AgNPs-NDG) was prepared and used to construct a novel sensitive sensor for the voltammetric determination of thioridazine (TR). The results indicate a remarkable increase in the oxidation peak currents together with a negative shift in the oxidation peak potentials, in comparison to the bare pyrolytic graphite electrode. Remarkable enhancement in microscopic area of the electrode along with strong adsorption of TR on the surface of the modified electrode resulted in a considerable increase in the peak current of TR. The surface morphology and the nature of the composite film deposited on PGE were characterized by scanning electron... 

    Nanoparticulate hollow TiO 2 fibers as light scatterers in dye-sensitized solar cells: Layer-by-layer self-assembly parameters and mechanism

    , Article ChemPhysChem ; Volume 12, Issue 5 , 2011 , Pages 966-973 ; 14394235 (ISSN) Rahman, M ; Tajabadi, F ; Shooshtari, L ; Taghavinia, N ; Sharif University of Technology
    Hollow structures show both light scattering and light trapping, which makes them promising for dye-sensitized solar cell (DSSC) applications. In this work, nanoparticulate hollow TiO 2 fibers are prepared by layer-by-layer (LbL) self-assembly deposition of TiO 2 nanoparticles on natural cellulose fibers as template, followed by thermal removal of the template. The effect of LbL parameters such as the type and molecular weight of polyelectrolyte, number of dip cycles, and the TiO 2 dispersion (amorphous or crystalline sol) are investigated. LbL deposition with weak polyelectrolytes (polyethylenimine, PEI) gives greater nanoparticle deposition yield compared to strong polyelectrolytes... 

    Preparation of a cuins2 nanoparticle ink and application in a selenization-free, solution-processed superstrate solar cell

    , Article European Journal of Inorganic Chemistry ; Volume 2015, Issue 35 , November , 2015 , Pages 5793–5800 ; 14341948 (ISSN) Cheshme Khavar, A. H ; Mahjoub, A. R ; Tajabadi, F ; Dehghani, M ; Taghavinia, N ; Sharif University of Technology
    Wiley-VCH Verlag  2015
    We report a study on chalcopyrite solar cells fabricated by low-cost, nonvacuum, and selenization-free methods. Superstrate-type CuInS2 (CIS) thin-film solar cells were prepared by sequential ink deposition. The CIS film was formed from a stable low-carbon ink, which was synthesized at low temperature (<120 °C). The CIS nanoparticle ink was prepared with n-butylamine and acetic acid as the solvent and stabilizer, respectively. The viscous and stable ink that formed through the dispersion of the final nanoparticles in N,N-dimethylformamide (DMF) could be deposited readily onto the substrate. The major features of the obtained ink are the small amount of impurity phases and negligible carbon... 

    Investigation of the structure and electrical properties of strontium titanate thin films growth by pulsed laser deposition method

    , Article Journal of Ceramic Processing Research ; Volume 17, Issue 1 , 2016 , Pages 26-29 ; 12299162 (ISSN) Dehshali, M. B ; Mahdavi, S. M ; Tahmasebi, N ; Sharif University of Technology
    Hanyang University  2016
    In this paper, we have studied the properties of SrTiO3 thin films which have been deposited on Si/Ti/Pt substrates using pulsed laser deposition technique. The as-deposited films were annealed at temperature of 700 °C in oxygen environment for 1 h. The surface morphology, crystalline phase and chemical composition of the films were characterized by AFM, XRD and XPS techniques, respectively. The XRD data show that phase transition from amorphous to polycrystalline structure happens and also the lattice constant enhances during annealing process. This enhancement can be related to oxygen vacancies in thin films. The XPS data show partial lack of titanium atoms on the surface. The AFM analysis... 

    A three-step method for the deposition of large cuboids of organic–inorganic perovskite and application in solar cells

    , Article ChemPhysChem ; 2016 , Pages 2389-2394 ; 14394235 (ISSN) Shahbazi, S ; Malekshahi Byranvand, M ; Tajabadi, F ; Afshar, Sh ; Taghavinia, N ; Sharif University of Technology
    Wiley-VCH Verlag 
    A three-step method for the deposition of CH3NH3PbI3 perovskite films with a high crystalline structure and large cuboid overlayer morphology is reported. The method includes PbI2 deposition, which is followed by dipping into a solution of C4H9NH3I (BAI) and (BA)2PbI4 perovskite formation. In the final step, the poorly thermodynamically stable (BA)2PbI4 phase converts into the more stable CH3NH3PbI3 perovskite by dipping into a solution of CH3NH3I. The final product is characterized by XRD, SEM, UV/Vis, and photoluminescence analysis methods. The experimental results indicate that the prepared perovskite has cuboids with high crystallinity and large sizes (up to 1 μm), as confirmed by XRD... 

    Synthesis and characterization of polyamide membrane for the separation of acetic acid from water using RO process

    , Article Membrane Water Treatment ; Volume 8, Issue 4 , 2017 , Pages 323-336 ; 20058624 (ISSN) Mirfarah, H ; Mousavi, S. A ; Mortazavi, S. S ; Sadeghi, M ; Bastani, D ; Sharif University of Technology
    Techno Press  2017
    The main challenge in many applications of acetic acid is acid dehydration and its recovery from wastewater streams. Therefore, the performance of polyamide thin film composite is evaluated to separate acetic acid from water. To reach this goal, the formation of polyamide layer on polysulfone support membrane was investigated via interfacial polymerization (IP) of meta-phenylenediamine (MPD) in water with trimesoyl chloride (TMC) in hexane. Also, the effect of synthesis conditions, such as concentration of monomers and curing temperature on separation of acetic acid from water were investigated by reverse osmosis process. Moreover, the separation mechanism was discussed. The solute... 

    N-doped ZnO-CuO nanocomposite prepared by one-step ultrasonic spray pyrolysis and its photocatalytic activity

    , Article Chemical Physics Letters ; Volume 705 , 2018 , Pages 19-22 ; 00092614 (ISSN) Rahemi Ardekani, S ; Sabour Rouhaghdam, A ; Nazari, M ; Sharif University of Technology
    Elsevier B.V  2018
    Nanocomposite thin film of N-doped ZnO-CuO was deposited on glass substrate using ultrasonic spray pyrolysis method. Zinc acetate, copper acetate and ammonium acetate with different molar ratios were dissolved in water and used as precursors. A crumpled-shape morphology consisting of nanometer-sized particles was observed with FESEM. The elemental composition was evaluated with EDX analysis and the presence of nitrogen, oxygen, copper and zinc was confirmed. XRD analysis revealed the presence of ZnO and CuO crystalline phases with crystallite size of about 18 nm. The prepared nanocomposites exhibited high photocatalytic activity in degradation of methyl orange under UV light irradiation. ©... 

    The effect of grain size on the fluctuation-induced conductivity of Cu 1-xTlxBa2Ca3Cu4O 12-δ superconductor thin films

    , Article Superconductor Science and Technology ; Volume 20, Issue 8 , 2007 , Pages 742-747 ; 09532048 (ISSN) Khurram, A. A ; Mumtaz, M ; Khan, N.A ; Ahadian, M. M ; Iraji Zad, A ; Sharif University of Technology
    The high temperature superconductor thin films Cu1-xTl xBa2Ca3Cu4O12-δ (Cu1-xTlx- 1234) are post-annealed in a nitrogen atmosphere. The zero-resistivity critical temperature (Tc(R ≤ 0)) of these thin films is increased from 92.3 to 104K. The grain size is enhanced and their morphology is improved with the post-annealing. The enlargement of grain size is linked to fluctuation-induced conductivity (FIC) in the light of Aslamazov-Larkin (AL) theory. The FIC measurements have shown that the cross-over of three-dimensional (3D) to two-dimensional (2D) behaviour of fluctuations is shifted to higher temperature values with an increase of post-annealing temperature. These results have shown that the... 

    Modeling of J sc and V oc versus the grain size in CdTe, CZTS and Perovskite thin film solar cells

    , Article Superlattices and Microstructures ; Volume 128 , 2019 , Pages 421-427 ; 07496036 (ISSN) Nazem, H ; Pourasiab Dizaj, H ; Gorji, N. E ; Sharif University of Technology
    Academic Press  2019
    A modeling approach is presented for the first time to model the dependence of short-circuit current density (J sc ) and open-circuit voltage (V oc ) on the grain size g in three thin film solar cells including the emerging perovskites. The variation of J sc and V oc with the grain size (g) of three different solar cells with CdTe, CZTS and perovskite absorber layers are modelled and fitted with the experimental dataset collected from relevant literature. The experimental literature suggested that the grain size of absorber layers in solar cells is controlled during the deposition process by adjusting the growth rate, temperature and ambient. The model has been successfully applied to the... 

    Novel in-line effective fiber polarizer based on chromium and gold nano metal films: design and experiment

    , Article Laser Physics ; Volume 27, Issue 1 , 2017 ; 1054660X (ISSN) Yahyaei, B ; Panahi, O ; Malekmohamadi, S ; Mousavi, M ; Mardiha, M ; Kheyrollahi, M ; Sharif University of Technology
    The performance of the magnesium fluoride/chromium/gold in-line fiber optic polarizer on the thickness of magnesium fluoride buffer layer and chromium metal thin film was theoretically investigated. To prove the theoretical study, the magnesium fluoride/chromium/gold polarizer was made based on the simulation results. The obtained polarizer showed an extinction ratio of about 40 dB which is in a good agreement with the theoretical result at the corresponding thicknesses. Both theoretical and experimental results showed that by covering the side polished single mode fiber with the optimum layer thicknesses, a novel and an efficient fiber polarizer with the high extinction ratio could be... 

    Plasmonic fractals: Ultrabroadband light trapping in thin film solar cells by a Sierpinski nanocarpet

    , Article Optical and Quantum Electronics ; Vol. 46, issue. 6 , 2014 , pp. 751-757 ; ISSN: 03068919 Kazerooni, H ; Khavasi, A ; Sharif University of Technology
    Plasmonic Sierpinski nanocarpet as back structure for a thin film Si solar cell is investigated. We demonstrate that ultra-broadband light trapping can be obtained by placing square metallic nanoridges with Sierpinski pattern on the back contact of the thin film solar cell. The multiple-scale plasmonic fractal structure allows excitation of localized surface plasmons and surface plasmon polaritons in multiple wavelengths leading to obvious absorption enhancements in a wide frequency range. Full wave simulations show that 109 % increase of the short-circuit current density for a 200 nm thick solar cell, is achievable by the proposed fractal back structure. The amount of light absorbed in the... 

    MWCNT/WO3 nanocomposite photoanode for visible light induced water splitting

    , Article Journal of Solid State Chemistry ; Volume 204 , 2013 , Pages 341-347 ; 00224596 (ISSN) Yousefzadeh, S ; Reyhani, A ; Naseri, N ; Moshfegh, A. Z ; Sharif University of Technology
    The Multi-walled carbon nanotube (MWCNT)/WO3 nanocomposite thin films with different MWCNT's weight percentages were prepared by sol-gel method as visible light induced photoanode in water splitting reaction. Weight percentage of MWCNT in the all nanocomposite thin films was confirmed by TGA/DSC analysis. According to XPS analysis, oxygenated groups at the surface of the MWCNT and stoichiometric formation of WO3 thin films were determined, while the crystalline structure of the nanocomposite samples was studied by XRD indicating (0 0 2) peak of MWCNT in the monoclinic phase of WO3. The influence of different weight percentage (wt%) of MWCNT on WO3 photoactivity showed that the electron... 

    Micron-scale rod-like scattering particles for light trapping in nanostructured thin film solar cells

    , Article RSC Advances ; Volume 5, Issue 105 , 2015 , Pages 86050-86055 ; 20462069 (ISSN) Malekshahi Byranvand, M ; Taghavinia, N ; Nemati Kharat, A ; Dabirian, A ; Sharif University of Technology
    Royal Society of Chemistry  2015
    Spherical dielectric particles, nanofibers, and nanorods have been widely used as embedded scattering objects in nanostructured thin film solar cells. Here we propose micron-scale rod-like dielectric particles as a more effective alternative to the spherical ones for light trapping in thin film solar cells. The superior performance of these micro-rods is attributed to their larger scattering efficiency relative to the spherical particles as evidenced by full-wave optical calculations. Using a one-pot process, 1.7 μm-long bullet-shaped silica rods with 330 nm diameter are synthesized and their concentration in a N719-sensitized solar cell is optimized. A solar cell with an optimal... 

    An investigation of the surface morphology of nanostructured nickel thin films prepared by electrodeposition

    , Article International Journal of Surface Science and Engineering ; Volume 10, Issue 5 , 2016 , Pages 444-455 ; 1749785X (ISSN) Torabi, M ; Dolati, A ; Sharif University of Technology
    Inderscience Enterprises Ltd 
    Nickel nanostructure thin films were electrodeposited on copper plates to investigate the fractal study. Scharifker's equations were derived for instantaneous and progressive nucleation and 3D growth of hemispherical centres under diffusion-controlled condition to calculate in situ change of fractal dimension of surface. It was assumed that the layer could be formed completely when fractal dimension of surface inclined to 2. Moreover, the fractal analysis of atomic force microscopy (AFM) images has confirmed the presumed model. Also, the power values of power spectral density (PSD) of the AFM images were determined using fast Fourier transform (FFT) algorithms. The PSD plots are approximated... 

    Highly textured ZnO thin films: An economical fabrication, doping by Mn2+ and Sn2+ and approachment for optical devices

    , Article Materials and Design ; Volume 28, Issue 3 , 2007 , Pages 1065-1070 ; 02613069 (ISSN) Vaezi, M. R ; Sadrnezhaad, S. K ; Sharif University of Technology
    Elsevier Ltd  2007
    Fabrication of high quality zinc oxide thin films and analysis on its physical, chemical properties have applications in opto-electronic devices, UV laser, microelectronics and micro-machining schemes. Highly textured ZnO thin film with a preferred (0 0 2) orientation was prepared by two-stage chemical deposition (TSCD) using an aqueous solution containing zinc complex on a soda-lime glass substrate. From the results obtained, it can be shown that the preferred orientations of the film microcrystal changes with the doping process. The film was characterized by X-ray diffraction (XRD), SEM, EDAX, optical technique, Fourier transform infrared spectroscopy (FTIR) in order to qualify its... 

    Preparation and characterization of nanostructured TiO2thin film codoped with nitrogen and vanadium on glass surface by sol–gel dip-coating method

    , Article Research on Chemical Intermediates ; 2014 ; ISSN: 09226168 Khatibnezhad, H ; Sani, M. A. F ; Sharif University of Technology
    To enhance hydrophilicity and photocatalytic activity, N-doped and N–V-codoped TiO2films were coated on glass substrates by the sol–gel dip-coating method. The substrates were previously coated with SiO2using the same method. The coated samples, after annealing at 450 °C for 30 min in air, were analyzed by an X-ray diffractometer, scanning electron microscope, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, and UV–visible spectroscope. The SiO2/N–V-codoped TiO2photocatalyst showed a narrower band gap (2.93 eV) compared to the SiO2/N-doped. Degradation tests, methyl orange under UV light and stearic acid under visible light, were performed in order to evaluate... 

    Dewetting of evaporating thin films over nanometer-scale topographies

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Vol. 90, issue. 1 , July , 2014 ; ISSN: 15393755 Akbarzadeh, A. M ; Moosavi, A ; Moghimi Kheirabadi, A ; Sharif University of Technology
    A lubrication model is used to study dewetting of an evaporating thin film layer over a solid substrate with a nanometer-scale topography. The effects of the geometry of the topography, the contact angle, the film thickness, and the slippage on the dewetting have been studied. Our results reveal that the evaporation enhances the dewetting process and reduces the depinning time over the topography. Also it is shown that the depinning time is inversely proportional to the slippage and increasing the contact angle may considerably reduce the depinning time, while the film thickness increases the depinning time