Search for: atomic-force-microscopy
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    Height fluctuations and intermittency of V2O5 films by atomic force microscopy

    , Article Journal of Physics Condensed Matter ; Volume 15, Issue 12 , 2003 , Pages 1889-1898 ; 09538984 (ISSN) Iraji Zad, A ; Kavei, G ; Rahimi Tabar, M. R ; Vaez Allaei, S. M ; Sharif University of Technology
    The spatial scaling law and intermittency of the V2O5 surface roughness has been investigated by atomic force microscopy. The intermittency of the height fluctuations has been checked by two different methods, first, by measuring the scaling exponent of the qth moment of height-difference fluctuations i.e. Cq = <|h(x1) - h(x2)|q>, and second, by defining the generating function Z(q, N) and generalized multi-fractal dimension Dq. These methods predict that there is no intermittency in the height fluctuations. The observed roughness and dynamical exponents can be explained by numerical simulation on the basis of the forced Kuramoto-Sivashinsky equation  

    Characterization of polymeric membranes for membrane distillation using atomic force microscopy

    , Article Desalination and Water Treatment ; Volume 51, Issue 31-33 , 2013 , Pages 6003-6008 ; 19443994 (ISSN) Shirazi, M. M ; Bastani, D ; Kargari, A ; Tabatabaei, M ; Sharif University of Technology
    Taylor and Francis Inc  2013
    As membrane distillation (MD) is an under-developed separation process, specific membranes for MD applications are not yet commercially available. Therefore, microporous polymeric membranes made of hydrophobic materials fabricated for microfiltration purposes are usually used for MD applications. Characterization of such kind of membranes is important in order to achieve a better in-depth understanding of their performance and to fabricate specific membranes for MD process. One of the emerging characterization methods is atomic force microscopy (AFM) analysis. AFM is a newly developed high-resolution method that is useful for studying the surface topography of various types of membranes, and... 

    Stereometric and fractal analysis of sputtered Ag-Cu thin films

    , Article Surfaces and Interfaces ; Volume 21 , 2020 Ţălu, Ş ; Matos, R. S ; Pinto, E. P ; Rezaee, S ; Mardani, M ; Sharif University of Technology
    Elsevier B.V  2020
    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... 

    Co surface modification by bias sputtering in Cu/Co(Vb)/NiO/ Si(100) magnetic multilayer structures

    , Article Physica Status Solidi C: Conferences ; Volume 1, Issue 7 , 2004 , Pages 1744-1747 ; 16101634 (ISSN) Moshfegh, A. Z ; Sangpour, P ; Sharif University of Technology
    To investigate the Ta/Co/Cu/Co/NiO/Si(100) spin valve structure, fabrication and characterization of the Cu/Co/NiO/Si(100) system was studied for further understanding the structure. The system was grown by employing combinative DC sputtering-evaporation technique. Nickel oxide with a thickness of about 30 nm was deposited on Si(100) substrate using thermal evaporation technique.The cobalt film, then, with a thickness of about 3 nm was grown by DC sputtering under various applied negative bias voltages ranging from 0 to - 80 V. The optimum bias voltage (Vb = -60 V) for the growth of Co layer was determined by atomic force microscopy (AFM), four-point probe sheet measurement (Rs) and scanning... 

    Stochastic analysis and regeneration of rough surfaces

    , Article Physical Review Letters ; Volume 91, Issue 22 , 2003 ; 00319007 (ISSN) Jafari, G.R ; Fazeli, S. M ; Ghasemi, F ; Vaez Allaei, S. M ; Rahimi Tabar, M ; Iraji zad, A ; Kavei, G ; Sharif University of Technology
    We investigate the Markov property of rough surfaces. Using stochastic analysis, we characterize the complexity of the surface roughness by means of a Fokker-Planck or Langevin equation. The obtained Langevin equation enables us to regenerate surfaces with similar statistical properties compared with the observed morphology by atomic force microscopy. © 2003 The American Physical Society  

    Simulation of Imaging in Trolling Mode Atomic Force Microscopy by Molecular Dynamics Method

    , M.Sc. Thesis Sharif University of Technology Abdi Nemat Abad, Ahmad (Author) ; Nejat Pishkenari, Hossein (Supervisor)
    Atomic force microscopy (AFM), as an indispensable tool for nanoscale characterization, has major drawback for operation in a liquid environment arising from the large hydrodynamic drag on the vibrating cantilever. The newly introduced “Trolling Mode” (TR-Mode) AFM resolves this complication utilizing a specialized nanoneedle cantilever that keeps the cantilever outside of the liquid. Herein, a mechanical model with a lumped mass was developed to capture the dynamics of such cantilever with a nanoneedle tip. This new developed model was applied to investigate the effects of the needle – liquid interface on the performance of the AFM, including the imaging capability in liquid. Also... 

    Dynamic Modeling and Control of Atomic Force Microscope in Trolling Mode

    , Ph.D. Dissertation Sharif University of Technology Sajadi, Mohammad Reza (Author) ; Vosoughi, Gholamreza (Supervisor) ; Nejat Pishkenari, Hossein (Supervisor)
    Trolling mode atomic force microscope (TR-AFM) significantly reduces the hydrodynamic drag generated during operation in liquid environments. This is achieved by utilizing a long nanoneedle and keeping the cantilever out of liquid. In this research, a continuous mathematical model is developed to study TR-AFM dynamics near a sample submerged in the liquid. Effects of cantilever torsion, nanoneedle flexibility, and liquid-nanoneedle interactions are considered in the model. The finite element model of the TR-AFM resonator considering the effects of fluid and nanoneedle flexibility is presented in this research, for the first time. The model is verified by ABAQUS software. The effect of... 

    Determination of the Surface Properties and Topography in AFM Using System Dynamics

    , M.Sc. Thesis Sharif University of Technology Seifnejad Haghighi, Milad (Author) ; Nejat, Hossein (Supervisor)
    Nowadays, the atomic force microscopy (AFM) has become a useful laboratory tool with variety of applications. In the traditional imaging technique, usually the amplitude or frequency of AFM tip oscillations is set at a desired value using a feedback control system which is a relatively slow process. In the current research, we propose an estimation approach which uses an adaptive fading extended Kalman filter (augmented with forgetting factor) as a system observer and couples with the system dynamics to determine the sample topography. As a result, in addition to state variables of system dynamic, the sample height as an unknown parameter is estimated with high accuracy in a relatively short... 

    Modeling of Force Interactions between Tip of Atomic Force Microscopy in Trolling Mode and Environment

    , M.Sc. Thesis Sharif University of Technology Falsafi, Ali (Author) ; Nejat Pishkenari, Hossein (Supervisor)
    Submerging of the Micro-beam of the AFM is indispensible in case of imaging bio-samples. (Bio-samples are unstable in non-aquos environment.), so hydrodynamical interaction of liquid and beam (viscous and meniscus forces) will result into quality factor decrease. This will cause image resolution decrement as well as damage to the sample because of large tip-sample forces during imaging of the bio-samples. The proposed method “Trolling mode AFM” keeps the micro-beam of the AFM out of the liquid, by adding a nano-needle to the end of the AFM tip. This would lead to resolve the aforementioned problems. Modeling of a part of the operation of this mechanism was done in this thesis, in order to... 

    Atomic interactions between metallic tips and surfaces in NC-AFM

    , Article Journal of Physics D: Applied Physics ; Volume 48, Issue 12 , February , 2015 ; 00223727 (ISSN) Pishkenari, H. N ; Sharif University of Technology
    Institute of Physics Publishing  2015
    In this paper, the atomic-scale interactions between metallic tips and samples in noncontact atomic force microscopy (NC-AFM) are studied using molecular dynamics simulations. The effects of the tip and sample materials, the surface plane direction and the lateral position of the tip with respect to the sample, on the interaction force and the dissipated energy, are investigated. The simulations conducted demonstrate that, generally, we can classify the possible outcomes for the dynamics due to the tip-surface interactions into four major categories. The first category includes all cases in which there are no considerable instabilities in tip-surface interactions, leading to negligible... 

    Evaluation of the topographical surface changes of silicon wafers after annealing and plasma cleaning

    , Article Silicon ; Volume 12, Issue 11 , 2020 , Pages 2563-2570 Stach, S ; Ţălu, Ş ; Dallaev, R ; Arman, A ; Sobola, D ; Salerno, M ; Sharif University of Technology
    Springer Science+Business Media B.V  2020
    Purpose: The morphological stability of silicon single crystal wafers was investigated, after performing cleaning surface treatments based on moderate temperature annealing and plasma sputtering. Methods: The wafer surfaces were measured by Tapping mode atomic force microscopy in air, before and after the different treatments. The 3D images were segmented by watershed algorithm identifying the local peaks, and the stereometric parameters were extracted thereof. The analysis of variance allowed to better assess the statistically significant differences. Results: All the resulting quantities were critically discussed. It appeared that the different cleaning treatments affected differently the... 

    Dynamics of the nanoneedle probe in trolling mode AFM

    , Article Nanotechnology ; Volume 26, Issue 20 , April , 2015 ; 09574484 (ISSN) Abdi, A ; Pishkenari, H. N ; Keramati, R ; Minary Jolandan, M ; Sharif University of Technology
    Institute of Physics Publishing  2015
    Atomic force microscopy (AFM), as an indispensable tool for nanoscale characterization, presents major drawbacks for operation in a liquid environment arising from the large hydrodynamic drag on the vibrating cantilever. The newly introduced 'Trolling mode' (TR-mode) AFM resolves this complication by using a specialized nanoneedle cantilever that keeps the cantilever outside of the liquid. Herein, a mechanical model with a lumped mass was developed to capture the dynamics of such a cantilever with a nanoneedle tip. This new developed model was applied to investigate the effects of the needle-liquid interface on the performance of the AFM, including the imaging capability in liquid  

    Chaos control in continuous mode of T-AFM systems using nonlinear delayed feedback via sliding mode control

    , Article ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, Seattle, WA, 11 November 2007 through 15 November 2007 ; Volume 11 PART A , 2008 , Pages 201-208 ; 079184305X (ISBN); 9780791843055 (ISBN) Sadeghian, H ; Salaried, H ; Alasty, A ; Sharif University of Technology
    The taping mode Atomic Force Microscopic (T-AFM) can be assumed as a cantilever beam which its base is excited by a sinusoidal force and nonlinear potential interaction with sample. Thus the cantilever may cause chaotic behavior which decreases the performance of the sample topography. In order to modeling, using the galerkin method, the PDE equation is reduced to a single ODE equation which properly describing the continuous beam. In this paper a nonlinear delayed feedback control is proposed to control chaos in T-AFM system. Assuming model parameters uncertainties, the first order Unstable Periodic Orbits (UPOs) of the system is stabilized using the sliding nonlinear delayed feedback... 

    The fractal study of Cu-Ni layer accumulation during electrodeposition under diffusion-controlled condition

    , Article Materials Research Bulletin ; Volume 42, Issue 9 , 2007 , Pages 1769-1776 ; 00255408 (ISSN) Nouri, E ; Dolati, A ; Sharif University of Technology
    The fractal study of thin layer films has been concerned by numerous studies, but it is a novel idea to use this method for interpretation of layer formation during electrocrystallization, simultaneously. In present study, Scharifker's equations were derived for instantaneous and progressive nucleation and 3D growth of hemispherical centers 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 AFM images has confirmed the presumed model. © 2006 Elsevier Ltd. All rights reserved  

    Etched glass surfaces, atomic force microscopy and stochastic analysis

    , Article Physica A: Statistical Mechanics and its Applications ; Volume 375, Issue 1 , 2007 , Pages 239-246 ; 03784371 (ISSN) Jafari, G. R ; Reza Rahimi Tabar, M ; Iraji zad, A ; Kavei, G ; Sharif University of Technology
    The effect of etching time scale of glass surface on its statistical properties has been studied using atomic force microscopy technique. We have characterized the complexity of the height fluctuation of an etched surface by the stochastic parameters such as intermittency exponents, roughness, roughness exponents, drift and diffusion coefficients and found their widths in terms of the etching time. © 2006 Elsevier B.V. All rights reserved  

    On the growth sequence of highly ordered nanoporous anodic aluminium oxide

    , Article Materials and Design ; Volume 27, Issue 10 , 2006 , Pages 983-988 ; 02613069 (ISSN) Ghorbani, M ; Nasirpouri, F ; Iraji zad, A ; Saedi, A ; Sharif University of Technology
    Elsevier Ltd  2006
    Anodic aluminium oxide films were fabricated by well known two-step anodizing process in oxalic acid electrolyte. The ordering characteristics (ordered pore domains, average pore diameter size and through-pore arrangement) of anodic aluminium oxide films, obtained in different growth sequences, were identified by microscopic analysis such as ex situ contact-mode atomic force microcopy and scanning electron microscopy. Flattened areas in which some pits are seen mostly cover the electropolished surface of aluminium. Single anodizing of aluminium produces a broad distribution of nanopore size, whereas induces a highly ordered hemispherical pattern, which plays the ordered nucleation sites for... 

    Effects of axial load on wave propagation in double-walled carbon nanotubes used as a flexible tip in AFM

    , Article DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Long Beach, CA, 24 September 2005 through 28 September 2005 ; Volume 1 A , 2005 , Pages 433-439 ; 0791847381 (ISBN); 9780791847381 (ISBN) Dalir, H ; Hatsuzawa, T ; Akbari, J ; Farshidianfar, A ; Sharif University of Technology
    American Society of Mechanical Engineers  2005
    This paper is concerned with the effect of axial load, shear deformation and rotary inertia on wave propagation in double-walled carbon nanotubes (DWCNTs) within terahertz range. Our analysis is based on Timoshenko-beam model and Eulerbeam model. The present models predict some terahertz critical frequencies at which the number of wave speeds changes. In these models the amounts of wave speed is unique only when the frequency is below the lowest critical frequency. When the frequency is equal to the lowest critical frequency, there can be one or two (for CNTs of smaller radii) wave speeds. Furthermore, when the frequency is higher than the lowest critical frequency, more than one wave speed... 

    Dynamic and Vibration Analysis of Non-Rotating and Rotating FGM Cantilever Beams Under Moving Mass

    , M.Sc. Thesis Sharif University of Technology Rahaeifard, Masoud (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Hoviattalab, Maryam (Supervisor)
    The purpose of this work, is to design a cantilever arm made of functionally graded materials so that the arm has maximum natural frequency and minimum mass. In this work the arm is modeled by Euler-Bernoulli beam theory and properties are assumed to be varying through the thickness. The beam is considered to be made of Aluminum and Alumina as metal and ceramic respectively and Genetic Algorithm method is used for optimization step. Finally using FGMs in atomic force microscopes is proposed as a new application of these materials  

    Nonlinear Distributed-Parameters Vibration Analysis of an AFM Microcantilever Beam in Dynamic Mode

    , Ph.D. Dissertation Sharif University of Technology Delnavaz, Aidin (Author) ; Zohoor, Hassan (Supervisor)
    Dynamic and vibration behavior of AFM microcantilever beam subject to the tip-sample interaction and/or contact is systematically investigated. An Euler-Bernoli microcantilever in 2D plane is considered with longitudinal and bending displacements. Inextensibility assumption and extended Hamilton’s principle is utilized to extract the single-variable integro partial equation of motion under: 1) tip-nanoparticle interactions, 2) tip-surface interactions in non-contact mode and 3) tip-surface interactions and contacts in intermittent-contact mode. Galerkin’s first mode approximation is then used to discretize the derived equations; and multiple time scales method is adopted to analyze the... 

    Investigation of Mechanical Properties of Graphene

    , Ph.D. Dissertation Sharif University of Technology Rasuli, Reza (Author) ; Iraji Zad, Azam (Supervisor) ; Rafii-tabar, Hashem (Supervisor)
    The unique properties of graphene due to the presence of massless Dirac fermions, high surface to volume ratio, high crystal quality in 2D, and high mechanical strength, recommend it as a promising material for technologies such as nanoelectromechanical systems (NEMS) and nanosensors. Use of graphene in nanodevices is accompanied by induced strains and stresses. Therefore it is important to study the mechanical properties of graphene. In present thesis, we synthesized graphene using both mechanical cleavage of graphite and chemical method. In the chemical method graphene oxide is prepared by oxidation and exfoliation of graphite. The graphene oxide sheets were reduced to prepare graphene...