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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 ; Moosavi, A ; Moghimi Kheirabadi, A ; Sharif University of Technology
Abstract
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
A Power-Law Relationship between Characteristics of Light Source and Quantum Yield in Photocatalytic Systems
, Article Journal of Physical Chemistry C ; Volume 119, Issue 39 , July , 2015 , Pages 22425-22431 ; 19327447 (ISSN) ; Sharif University of Technology
American Chemical Society
2015
Abstract
A new dimensionless parameter, Sh-factor, is introduced by using dimensional analysis and extending the quantum yield definition to show power-law relations among light intensity, light wavelength, distance from light source, concentrations of dye/pollutant and photocatalyst, time, and degradation percent. The Sh-factor has the same equation form for photoactivated remediation systems with particulate and thin-film photocatalysts, and it provides mathematical tools to predict degradation performance of a photocatalytic system. These power-law equations separate simply the operational parameters related to the lamp from semiconductor photocatalyst characteristics. The light scattering and...
SnO2/ZnO double layer thin films: A novel economical preparation and investigation of sensitivity and stability of double layer gas sensors
, Article International Journal of Nanomanufacturing ; Volume 2, Issue 1-2 , 2008 , Pages 59-69 ; 17469392 (ISSN) ; Shokuhfar, A ; Sadrnezhaad, S. K ; Shokuhfar, T ; Sharif University of Technology
Inderscience Publishers
2008
Abstract
A double-layer SnO2/ZnO gas sensor was produced by utilisation of SnOSUB align=right2 and ZnO thin films. Top layer consisted of SnOSUB align=right2 produced by a sol gel-controlled annealing technique. Bottom coating consisted of ZnO thin film precipitated by Two-Stage Chemical Deposition (TSCD) from an aqueous zinc-containing solution. Both top and bottom coatings were analysed by SEM, XRD, EDAX and AAS. Gas sensitivity of the SnO2/ZnO double layer was determined by electrical resistance measurements. Although sensitivity was slightly reduced by double-layer formation, selectivity and stability were considerably improved by combination of the two thin layers. The existence of an...
Structure and composition of the segregated Cu in V 2 O 5 /Cu system
, Article Applied Surface Science ; Volume 253, Issue 5 , 2006 , Pages 2581-2588 ; 01694332 (ISSN) ; Iraji zad, A ; Sharif University of Technology
Elsevier
2006
Abstract
We have investigated segregation of copper at the surface of V 2 O 5 films deposited onto Cu substrate by employing surface analysis techniques. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) confirmed that the Cu is segregated at the surface and its chemical state is Cu 2 O. According to secondary ion mass spectroscopy (SIMS) and glow discharge spectroscopy (GDS), the Cu concentration inside the deposited V 2 O 5 layer is low. Ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS) revealed the segregation alters the surface local density of states. Surface analysis of deposited samples in ultra high vacuum (UHV) condition...
Investigation On Microstructure And Properties Of Barium Strontium Titanate Thin Films Grown By Pulsed Laser Deposition
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Mahdavi, Mohammad (Supervisor)
Abstract
Barium Strontium Titanate (BST) thin films are a promising candidate for dielectric capacitors due to their excellent ferroelectric properties. It is well known that BST has a high dielectric constant, low loss tangent, low leakage current and low Curie temperature. Pulse laser deposition (PLD) has been used extensively as it can maintain the stoichiometry of the target in the deposited film and also has high coverage ability, which both are important in capacitors. In this paper, Ba0.6Sr0.4TiO3 (BST) thin film has been deposited on the SiO2/Si substrate by pulsed laser deposition technique. The effect of post-annealed temperature, oxygen pressure deposition ambience and number of pulses on...
Synthesis and Antibacterial Activity of TiO2/ZnO Nanocomposite via Sol-Gel Method
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
The synthesis and usage of TiO2/ZnO nanocomposite thin film in antibacterial activity against E-coli were experimented through a systematic research. TiO2/ZnO nanocomposite films can demonstrate different properties like gas sensing, self cleaning and treatment of the broad range of aqueous pollutants when it is exposed to light with wavelengths less than 400 nm. This phenomenon happens because of the photocatalytic reactions in the nanocomposite thin film which cause active species production on the surface of the thin film. The nanocomposite synthesis was based on sol-gel process in atmospheric pressure. In this study titanium dioxide is prepared by sol gel method from titanium...
Electrical and Optical Properties of Doped (Ba, Sr)TiO3 Layers Prepared Via Sol-gel Method
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor)
Abstract
The main purpose of this research was simultaneous doping of carbon and nickel in the structure of barium strontium titanate, in order to investigate its dielectric and optical properties. Powders and films of BST, was synthesized by the sol-gel method in six different compositions: without any dopant, 0.04mol nickel dopant, 0.04mol nickel dopant accompanied by different amounts of carbon (0.01, 0.02, 0.03 and 0.04 mol). Suspensions were dip coated on alumina and quartz substrates. Structural features and chemical bonds, were studied through thermal analysis, XRD, FT-IR, FESEM and AFM. For electrical and optical properties, LCR-meter and UV-Vis were used. XRD and FESEM proved that nickel...
Numerical Investigation of Dewetting of Evaporating thin Films over Nanometric Topography
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Evaporation and condensation of thin films can rupture or stabilize thin film .We show that evaporation hastens dewetting of a thin film. Dewetting over nanometric downward step causes pinning of the contact line near the step. This phenomena is not permanent and after certain time that contact angle reaches to its critical value depinnnig happens. We also study the effect of the step size, contact angle, film thickness, slip and evaporation on the depinning time of the contact line. We show that depinnig time has a reverse relation with the rate of evaporation
Thin Film Thickness Measurement Using Colors of Interference Fringes
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor)
Abstract
There are several methods for measuring thin film thickness, however, for the analysis of liquid film motors [1] we need a method which is capable of measuring the thickness using a single image of the film. In this work, we use the colors that appear on thin films, such as soup bubbles, which is a result of light interference to calculate the thickness of the layer
Property change during nanosecond pulse laser annealing of amorphous NiTi thin film
, Article Bulletin of Materials Science ; Volume 35, Issue 3 , 2012 , Pages 357-364 ; 02504707 (ISSN) ; Yasavol, N ; Ganjali, M ; Sanjabi, S ; Sharif University of Technology
2012
Abstract
Nanosecond lasers of different intensities were pulsed into sputter-deposited amorphous thin films of near equiatomic Ni/Ti composition to produce partially crystallized highly sensitive R-phase spots surrounded by amorphous regions. Scanning electron microscopy having secondary and back-scattered electrons, field emission scanning electron microscopy, optical microscopy and X-ray diffraction patterns were used to characterize the laser treated spots. Effect of nanosecond pulse lasering on microstructure, morphology, thermal diffusion and inclusion formation was investigated. Increasing beam intensity and laser pulse-number promoted amorphous to R-phase transition. Lowering duration of the...
Theory of the liquid film motor
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 3 , September , 2015 ; 15393755 (ISSN) ; Namin, R. M ; Amjadi, A ; Sharif University of Technology
American Physical Society
2015
Abstract
The liquid film motor is a freely suspended liquid film placed between two capacitively coupled plates that rotates when an electric current is passed through it. Here we propose a theory for its rotation mechanism based on thin film electroconvection. The capacitively coupled plates induce free charges on the surfaces of the film, and the electric field on the film exerts a force that induces rotation. Results of the proposed theory and simulation are in good agreement with the experiments in different properties of the liquid film motor
Theoretical study of light trapping in nanostructured thin film solar cells using wavelength-scale silver particles
, Article ACS Applied Materials and Interfaces ; Volume 7, Issue 27 , July , 2015 , Pages 14926-14932 ; 19448244 (ISSN) ; Taghavinia, N ; Sharif University of Technology
American Chemical Society
2015
Abstract
We propose and theoretically evaluate a plasmonic light trapping solution for thin film photovoltaic devices that comprises a monolayer or a submonolayer of wavelength-scale silver particles. We systematically study the effect of silver particle size using full-wave electromagnetic simulations. We find that light trapping is significantly enhanced when wavelength-scale silver particles rather than the ones with subwavelength dimensions are used. We demonstrate that a densely packed monolayer of spherical 700 nm silver particles enhances integrated optical absorption under standard air mass 1.5 global (AM1.5G) in a 7 μm-thick N719-sensitized solar cell by 40% whereas enhancement is smaller...
Structural and optical properties of Pd 2+-doped mesoporous TiO 2 thin films prepared by sol-gel templating technique
, Article Optoelectronics and Advanced Materials, Rapid Communications ; Volume 4, Issue 10 , 2010 , Pages 1572-1577 ; 18426573 (ISSN) ; Sadrnezhaad, S. K ; Sharif University of Technology
2010
Abstract
Pd 2+-doped TiO 2 thin films with mesoporous structure were produced on quartz substrate by sol-gel dip coating. The structural, morphological and optical properties of the film were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV/vis transmittance spectroscopy. By increasing the Pd 2+ concentration from 0 to 6 mol%, the crystallites appeared solely as the anatase phase and their average sizes decreased from 10.5 to 7.1 nm. Addition of Pd 2+ also resulted in increasing of the specific surface area and decreasing of the pore size of the layer. The transmittance of the films decreased in the...
Influence of annealing temperature on structural and optical properties of mesoporous TiO2 thin films prepared by sol-gel templating technique
, Article Journal of Optoelectronics and Advanced Materials ; Volume 12, Issue 7 , 2010 , Pages 1490-1497 ; 14544164 (ISSN) ; Sadrnezhaad, S. K ; Sharif University of Technology
2010
Abstract
TiO2 thin films with mesoporous structure were deposited on quartz substrate by sol-gel dip coating. The structural, morphological and optical properties of the films were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV/Vis transmittance spectroscopy. Crystallization of the anatase phase was initiated at 300°C. Its transformation to the rutile phase occurred at 700°C. Anatase and rutile crystallites initially sized 3.2 and 15.3nm, respectively. The anatase phase was under tension; but the rutile phase was...
Comparison of the mechanical properties of NiTi/Cu bilayer by nanoindentation and tensile test: Molecular dynamics simulation
, Article Materials Research Express ; Volume 3, Issue 12 , 2016 ; 20531591 (ISSN) ; Vahedpour, M ; Sadrnezhaad, S. K ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
Molecular dynamics simulation was used to study of mechanical properties of NiTi/Cu bilayer by nanoindentation and tensile testing. A comparison has been made among mechanical properties measured and plastic deformation process at different copper thickness during nanoindnetation and tensile test of the samples. Embedded atom method potentials for describing of inter-Atomic interaction and Nose-Hoover thermostat and barostat are employed in the simulation at 400 K. The results showed that as the copper film thickness decreased, the maximum load and hardness values increased during nanoindetation. Saha and Nix model is used to describe reduced young's modulus behaviour of the bilayer system...
Self-assembled monolayer of wavelength-scale core-shell particles for low-loss plasmonic and broadband light trapping in solar cells
, Article ACS Applied Materials and Interfaces ; Volume 8, Issue 1 , 2016 , Pages 247-255 ; 19448244 (ISSN) ; Malekshahi Byranvand, M ; Naqavi, A ; Nemati Kharat, A ; Taghavinia, N ; Sharif University of Technology
American Chemical Society
Abstract
Scattering particles constitute a key light trapping solution for thin film photovoltaics where either the particles are embedded in the light absorbing layer or a thick layer of them is used as a reflector. Here we introduce a monolayer of wavelength-scale core-shell silica@Ag particles as a novel light trapping strategy for thin film photovoltaics. These particles show hybrid photonic-plasmonic resonance modes that scatter light strongly and with small parasitic absorption losses in Ag (<1.5%). In addition, their scattering efficiency does not vary significantly with the refractive index of the surrounding medium. A monolayer of these particles is applied as the top-scattering layers in a...
Mixed-Halide CH3NH3PbI3−xXx (X=Cl, Br, I) perovskites: vapor-assisted solution deposition and application as solar cell absorbers
, Article ChemPhysChem ; 2016 , Pages 2382-2388 ; 14394235 (ISSN) ; Tajabadi, F ; Shahbazi, S ; Gholipour, S ; Taghavinia, N ; Sharif University of Technology
Wiley-VCH Verlag
Abstract
There have been recent reports on the formation of single-halide perovskites, CH3NH3PbX3 (X=Cl, Br, I), by means of vapor-assisted solution processing. Herein, the successful formation of mixed-halide perovskites (CH3NH3PbI3−xXx) by means of a vapor-assisted solution method at ambient atmosphere is reported. The perovskite films are synthesized by exposing PbI2 film to CH3NH3X (X=I, Br, or Cl) vapor. The prepared perovskite films have uniform surfaces with good coverage, as confirmed by SEM images. The inclusion of chlorine and bromine into the structure leads to a lower temperature and shorter reaction time for optimum perovskite film formation. In the case of CH3NH3PbI3−xClx, the optimum...
SnO2 nanowires on carbon nanotube film as a high performance anode material for flexible Li-ion batteries
, Article Journal of Nanostructures ; Volume 8, Issue 3 , 2018 , Pages 288-293 ; 22517871 (ISSN) ; Faramarzi, M. S ; Sanaee, Z ; Ghasemi, S ; Sharif University of Technology
University of Kashan
2018
Abstract
Today, Li-ion batteries (LIBs) are the most common rechargeable batteries used in electronic devices. SnO2 with theoretical specific capacity of 782 mAh/g is among the best anode materials for LIBs. In this report, Threedimensional SnO2 nanowires (NWs) on carbon nanotube (CNT) thin film (SnO2 / CNT) is fabricated using a combination of vacuum filtration and thermal evaporation techniques. The resulting 3D heterostructure SnO2/CNT was characterized by X-ray diffraction, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This fabricated SnO2/CNT electrode has been tested as a flexible and binderfree anode for LIB, which exhibits high initial discharge/charge...
Stereometric and fractal analysis of sputtered Ag-Cu thin films
, Article Surfaces and Interfaces ; Volume 21 , 2020 ; Matos, R. S ; Pinto, E. P ; Rezaee, S ; Mardani, M ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this paper, we have successfully deposited Ag-Cu thin films. Nanoscale morphology and nanotexture were studied using atomic force microscopy (AFM) through fractal and stereometric parameters. Additional algorithms have been developed to study new fractal parameters such as surface entropy, fractal succolarity, and fractal lacunarity. The results revealed that as the deposition time increased, films exposed isotropies between ~65 and 82%, which were correlated to the fractal patterns, where from #3 to #5 there were greater spatial complexities. Moreover, surface roughness increased from #1 to #3, which was observed for both Sq and Sa. Similar behavior was exhibited by the other height...
The effect of addition of Tiron as a surfactant on the microstructure of chemically deposited zinc oxide
, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 128, Issue 1-3 , 2006 , Pages 53-57 ; 09215107 (ISSN) ; Vaezi, M. R ; Sharif University of Technology
2006
Abstract
The effect of one of the surfactants such as Tiron, a compound based on the benzene molecule, on the morphology and chemical composition of zinc oxide deposits, produced from a zinc complex solution using two-stage chemical deposition (TSCD) technique, has been investigated. TSCD technique is a novel and simple chemical route for the deposition of ZnO film from aqueous solution. Zinc oxide films deposited on high purity alumina (HPA) as a substrate. The results show that the addition of Tiron changes the surface morphology and causes to form the fine-grained structure. With a dense and nodular-shape appearance, the film produced from the precursor of zinc complex-containing Tiron, is...