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Khan, Umar. "Control of atomic force microscopes." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/372495/.
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Atomic force microscopes or AFMs are instruments which use a mechanical probe to scan a sample and estimate surface topography with nanometer accuracy. The term atomic force originates from the fact that the imaging process relies upon the existence of the inter-atomic interaction force between the mechanical probe and sample surface. These instruments have established themselves as a vital cutting edge tool for investigation of matter at the nanometer scale. Their widespread usage is due not only to their superior resolution but also because they can operate in any medium namely air, liquid and vacuum. Another major advantage is that, unlike their predecessor instruments AFMs do not require their samples to be conductive. This fact alone has enabled in situ imaging of biological samples with unprecedented resolution and without sample alteration. Other instruments like scanning electron microscopes (SEMs) can also view biological samples, however they require the samples to be prepared and dried. While some sample structure may be preserved, AFMs have no such limitation. Despite the fact that AFMs offer all these advantages, the usage of a mechanical probe for image generation causes them to be inherently reliant upon a feedback control loop. This is because the probe motion must be controlled in a suitable manner to avoid letting its motion dynamics distort the sample image. In addition, since the mechanical probe must be sequentially moved over the sample point by point, the imaging times are long and range from a few seconds to in excess of ten minutes. Given that feedback control is an integral part of AFM operation, the end users are forced to manually tune Proportaional-Integral (PI) controllers which are used in most commercial AFMs. Since the vast majority of scientists using AFMs do not necessarily possess a knowledge of feedback control, they do this tuning though a manual trial and error procedure which consumes valuable research time. Although the control systems community has taken considerable interest in AFM control, the methods suggested often require high order controllers and are tested for a specific experimental set up. The primary objective of this research is therefore to develop a novel automated controller synthesis mechanism which has the potential of being used in a diverse range of AFM setups. The method of choice for this research is Multiple Model Adaptive Control (MMAC). The motivation for this decision as well as experimental verification is provided in detail in this thesis. Given the wide commercial usage of PI controllers, the same are used as a starting point for this work. The applicability of the method suggested is however by no means restricted to them, and in the future can be extended to incorporate more sophisticated controllers, for instance robust controllers. The second objective of this research is to investigate two novel methods which have the potential of substantially reducing the AFM imaging time. The first one suggests coarser scan trajectories to save time, and then estimates the sample image using a relatively new signal processing method called Compressive Sensing. The second method suggested uses the AFM's mechanical probe in a novel manner that can also substantially reduce imaging time.
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El, Rifai Osamah M. "Modeling and control of undesirable dynamics in atomic force microscopes." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/38256.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (leaves 156-165).
The phenomenal resolution and versatility of the atomic force microscope (AFM), has made it a widely-used instrument in nanotechnology. In this thesis, a detailed model of AFM dynamics has been developed. It includes a new model for the piezoelectric scanner coupled longitudinal and lateral dynamics, creep, and hysteresis. Models for probe-sample interactions and cantilever dynamics were also included. The models were used to improve the dynamic response and hence image quality of contact-mode AFM. An extensive parametric study has been performed to experimentally analyze in-contact dynamics. Nonlinear variations in the frequency response were observed, in addition to changes in the pole-zero structure. The choice of scan parameters was found to have a major impact on image quality and feedback performance. Further, compensation for scanner creep was experimentally tested yielding a reduction in creep by a factor of 3 to 4 from the uncompensated system. Moreover, fundamental performance limitations in the AFM feedback system were identified. These limitations resulted in a severe bound on the maximum achievable feedback bandwidth, as well as a fundamental trade-off between step response overshoot and response time. A careful analysis has revealed that a PID controller has no real advantage over an integral controller.
(cont.) Therefore, a procedure for automatically selecting key scan parameters and controller gain was developed and experimentally tested for I-control. This approach, in contrast to the commonly used trial and error method, can substantially improve image quality and fidelity. In addition, a robust adaptive output controller (RAOC), was designed to guarantee global boundedness and asymptotic regulation in the presence and absence of disturbances, respectively. Simulations have shown that a substantial reduction in contact force can be achieved with the RAOC, in comparison with a well-tuned I-controller, yet with no increase in the maximum scan speed. Furthermore, a new method was developed to allow calibrating the scanner's vertical displacement up to its full range, in addition to characterizing scanner hysteresis. This work has identified and addressed crucial problems and proposed practical solutions to factors limiting the dynamic performance of the AFM.
by Osamah M. El Rifai.
Ph.D.
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Hui, Hui. "Contribution to a Simulator of Arrays of Atomic Force Microscopes." Thesis, Besançon, 2013. http://www.theses.fr/2013BESA2031/document.
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Dans cette thèse, nous établissons un modèle à deux échelles à la fois pour desmatrices de cantilevers unidimensionnels et bidimensionnels en régime de fonctionnementélastodynamique avec des applications possibles aux réseaux de microscopesà force atomique (AFM). Son élaboration est basée sur une analyseasymptotique pour les structures minces élastiques, une approximation à deuxéchelles et une mise à l’échelle utilisée pour l’homogénéisation des milieux fortementhétérogènes. Nous complétons la théorie de l’approximation à deux échellespour les problèmes aux limites du quatrième ordre posés dans des domaines mincespériodiques connexes seulement dans certaines directions. Notre modèle reproduitla dynamique globale du support ainsi que les mouvements locaux des cantilevers.Pour simplifier la suite du travail, nous concentrons nos travaux à l’étude de matricesde leviers constituées de lignes découplées en régime dynamique. Comme lesupport des leviers est élastique, l’effet du couplage entre levier est pris en compte.La vérification du modèle est soigneusement réalisée. Nous montrons que chaquemode propre peut être décomposé en produits d’un mode de base avec un modede levier. Nous présentons une méthode de discrétisation du modèle et effectuonssa vérification numérique en la comparant avec des résultats de simulation paréléments finis du problème d’élasticité tridimensionnel. Par ailleurs, nous avonsélaboré de nouveaux outils d’aide à la conception de réseaux d’AFM. Une boîte àoutils d’optimisation robuste est interfacée avec le modèle permettant d’optimiserun design avant micro-Fabrication. Un algorithme d’estimation de l’état statiquecombinant la mesure de déplacements mécaniques par interférométrie et le modèlea été introduit. Nous avons également synthétisé un régulateur quadratiquelinéaire (LQR) pour un réseau de cantilevers en mode dynamique comprenant actionneurset capteurs régulièrement espacées. Dans le but de mettre en oeuvre lecontrôle en temps réel, nous proposons une approximation semi-Décentralisée quipeut être réalisé par un circuit électronique distribué analogique. Plus précisément,notre processeur analogique peut être réalisé par un réseau périodique derésistances (PNR). La méthode d’approximation de commande est basée sur deuxconcepts généraux, à savoir sur un calcul fonctionnel (c’est-À-Dire des fonctionsd’opérateurs) et sur la formule de représentation d’une fonction d’opérateur deDunford-Schwartz. Cette méthode d’approximation est étendue pour la résolutiond’un problème de filtrage optimal robuste de type H∞ de la dynamique d’un réseaude leviers couplés avec sources aléatoires de bruitIn this dissertation, we establish a two-Scale model both for one-Dimensionaland two-Dimensional Cantilever Arrays in elastodynamic operating regime withpossible applications to Atomic Force Microscope (AFM) Arrays. Its derivationis based on an asymptotic analysis for thin elastic structures, a two-Scale approximationand a scaling used for strongly heterogeneous media homogenization. Wecomplete the theory of two-Scale approximation for fourth order boundary valueproblems posed in thin periodic domains connected in some directions only. Ourmodel reproduces the global dynamics as well as each of the cantilever motion. Forthe sake of simplicity, we present a simplified model of mechanical behavior of largecantilever arrays with decoupled rows in the dynamic operating regime. Since thesupporting bases are assumed to be elastic, cross-Talk effect between cantileversis taken into account. The verification of the model is carefully conducted. Weexplain not only how each eigenmode is decomposed into products of a base modewith a cantilever mode but also the method used for its discretization, and reportresults of its numerical validation with full three-Dimensional Finite Element simulations.We show new tools developed for Arrays of Microsystems and especiallyfor AFM array design. A robust optimization toolbox is interfaced to aid for designbefore the microfabrication process. A model based algorithm of static stateestimation using measurement of mechanical displacements by interferometry ispresented. We also synthesize a controller based on Linear Quadratic Regulator(LQR) methodology for a one-Dimensional cantilever array with regularly spacedactuators and sensors. With the purpose of implementing the control in real time,we propose a semi-Decentralized approximation that may be realized by an analogdistributed electronic circuit. More precisely, our analog processor is made by PeriodicNetwork of Resistances (PNR). The control approximation method is basedon two general concepts, namely on functions of operators and on the Dunford-Schwartz representation formula. This approximation method is extended to solvea robust H∞ filtering problem of the coupled cantilevers for time-Invariant systemwith random noise effects
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Cretegny, Laurent. "Use of atomic force microscopy for characterizing damage evolution during fatigue." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/20141.
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Leang, Kam K. "Iterative learning control of hysteresis in piezo-based nano-positioners : theory and application in atomic force microscopes /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/7127.
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Lawrence, Andrew James. "Development of a Hybrid Atomic Force and Scanning Magneto-Optic Kerr Effect Microscope for Investigation of Magnetic Domains." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/147.
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We present the development of a far-field magneto-optical Kerr effect microscope. An inverted optical microscope was constructed to accommodate Kerr imaging and atomic force microscopy. In Kerr microscopy, magnetic structure is investigated by measuring the polarization rotation of light reflected from a sample in the presence of a magnetic field. Atomic force microscopy makes use of a probe which is scanned over a sample surface to map the topography. The design was created virtually in SolidWorks, a three-dimensional computer-aided drafting environment, to ensure compatibility and function of the various components, both commercial and custom-machined, required for the operation of this instrument. The various aspects of the microscope are controlled by custom circuitry and a field programmable gate array data acquisition card at the direction of the control code written in National Instrument LabVIEW. The microscope has proven effective for both Kerr and atomic force microscopy. Kerr images are presented which reveal the bit structure of magneto-optical disks, as are atomic force micrographs of an AFM calibration grid. Also discussed is the future direction of this project, which entails improving the resolution of the instrument beyond the diffraction limit through near-field optical techniques. Preliminary work on fiber probe designs is presented along with probe fabrication work and the system modifications necessary to utilize such probes.
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Swinford, Richard William. "An AFM-SIMS Nano Tomography Acquisition System." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3485.
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An instrument, adding the capability to measure 3D volumetric chemical composition, has been constructed by me as a member of the Sánchez Nano Laboratory. The laboratory's in situ atomic force microscope (AFM) and secondary ion mass spectrometry systems (SIMS) are functional and integrated as one instrument. The SIMS utilizes a Ga focused ion beam (FIB) combined with a quadrupole mass analyzer. The AFM is comprised of a 6-axis stage, three coarse axes and three fine. The coarse stage is used for placing the AFM tip anywhere inside a (13x13x5 mm3) (xyz) volume. Thus the tip can be moved in and out of the FIB processing region with ease. The planned range for the Z-axis piezo was 60 µm, but was reduced after it was damaged from arc events. The repaired Z-axis piezo is now operated at a smaller nominal range of 18 µm (16.7 µm after pre-loading), still quite respectable for an AFM. The noise floor of the AFM is approximately 0.4 nm Rq. The voxel size for the combined instrument is targeted at 50 nm or larger. Thus 0.4 nm of xyz uncertainty is acceptable. The instrument has been used for analyzing samples using FIB beam currents of 250 pA and 5.75 nA. Coarse tip approaches can take a long time so an abbreviated technique is employed. Because of the relatively long thro of the Z piezo, the tip can be disengaged by deactivating the servo PID. Once disengaged, it can be moved laterally out of the way of the FIB-SIMS using the coarse stage. This instrument has been used to acquire volumetric data on AlTiC using AFM tip diameters of 18.9 nm and 30.6 nm. Acquisition times are very long, requiring multiple days to acquire a 50-image stack. New features to be added include auto stigmation, auto beam shift, more software automation, etc. Longer term upgrades to include a new lower voltage Z-piezo with strain-gauge feedback and a new design to extend the life for the coarse XY nano-positioners. This AFM-SIMS instrument, as constructed, has proven to be a great proof of concept vehicle. In the future it will be used to analyze micro fossils and it will also be used as a part of an intensive teaching curriculum.
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Boijoux, Romain. "Influence de l'élasticité du substrat sur la genèse, propagation et coalescence des structures de cloquage de revêtements et films minces." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI085.
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Le cloquage des films minces est un enjeu scientifique et industriel de premier plan, dans la mesure où il correspond au premier stade du délaminage a grande échelle du film, aboutissant généralement à la perte des propriétés fonctionnelles initialement conférées au matériau revêtu.L'influence de la souplesse du substrat sur ce phénomène est peu comprise à ce jour, alors que les systèmes industriels composés de films rigides sur substrats souples se multiplient. Cette étude se focalisera ainsi principalement sur l’influence de l’élasticité du substrat sur la genèse, propagation et coalescence des structures de cloquage, . L’approche expérimentale sera de générer des structures de cloquage élémentaires, de type ride droite, bulle ou « cordon de téléphone », et d’en contrôler la propagation, de manière à les faire interagir, se croiser, voire coalescer. La caractérisation morphologique de ces structures de cloquage se fera par microscopie à force atomique. Ces résultats expérimentaux seront confrontés à des simulations numériques par éléments finis réalisées en parallèle, permettant de tenir compte du couplage entre flambage du revêtement et délaminage de l’interface film/substrat. Les résultats obtenus permettront de mieux appréhender le phénomène de cloquage des revêtements et films minces. Cette étude répond ainsi principalement à trois questions : quelle est l’influence de l’élasticité du substrat sur la dynamique de propagation des cloques ? Comment se produisent leurs croisements aboutissant à des structures parfois singulières ? Cette élasticité favorise-t-elle la coalescence des cloques en cours de propagation, même si celles-ci ne se rencontreraient pas d’un point de vue purement balistique ?Enfin, l’intérêt technologique s’inscrit dans une démarche environnementale qui consiste à identifier les paramètres pertinents permettant d’inhiber le processus de cloquage, de le limiter, voire de le contrôler pour améliorer la durabilité des systèmes industrielsThin films buckling is a scientific and industrial challenge of primary importance, since it correspond to the first stage of the buckling of the film at a large scale, leading to the loss of the mechanical property initially conferred to the coated material.The influence of the substrate elasticity on this phenomenon is not well understood today, whereas the proportion of industrial systems made of rigid films on soft substrates increase. This study focus principally on the influence of the substrate elasticity on the genesis, propagation and coalescence of the buckled structures. The experimental approach consist in the controlled generation of elementary buckling structures, such as straight-sided buckles, blisters or “telephone cords” buckles, to make them interact and even meet and merge each other. The morphological characterization of such buckling structures will be performed by the atomic force microscopy technique. These experimental results will be then compared to finite elements simulations performed together, allowing to take into account the coupling between the buckling of the film and the film/substrate interface delamination. The obtained results will allow a better understanding of the coating and thin film buckling phenomenon. Thus, this study answer in particular to three questions : how the substrate elasticity impact the propagation dynamic of the buckles ? How their crossing occur, leading sometimes to complex structures ? Is this elasticity helps the coalescence of the buckles, even if they does not match each other in a “ballistic” way ?Finally, the technological goal is part of an environmental approach that consist in identifying the parameters that can suppress, limit or control the buckling phenomenon for specific applications
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Payton, Oliver David. "High-speed atomic force microscopy under the microscope." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574416.
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SINCE its invention in 1986, the atomic force microscope (AFM) has revolutionised the field of nanotechnology and nanoscience. It is a tool that has enabled research into areas of medicine, advanced materials, biology, chemistry and physics. However due to its low frame rate it is a tool that has been limited to imaging small areas using a time lapse technique. It has only been in recent years that the frame rate of the device has been increased in a tool known as high-speed AFM (HSAFM). This increased frame rate allows, for the first time, biological processes to be viewed in real time or macro sized areas to be imaged with nanoscale resolution. The research presented here concentrates on a specific type of high-speed AFM developed at the University of Bristol called contact mode HSAFM. This thesis explains how the microscope is able to function, and presents a leap in image quality due to an increased understanding of the dynamics of the system. The future of the device is also discussed. III
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Ewald, Maxime. "High speed bio atomic force microscopy : application à l'étude de la structure et dynamique d'assemblage supramoléculaires : étude des interactions au niveau de la cellule." Thesis, Dijon, 2011. http://www.theses.fr/2011DIJOS043.
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Le microscope à force atomique (AFM) fait partie des microscopies de champ proche dites à sonde locale. De par sa versatilité, un grand nombre de domaines des nanosciences tant en physique, que chimie ou biologie utilisent cette technique. Cependant, le champ d’investigation de la microscopie AFM classique est restreint temporellement et spatialement. En effet, en raison de sa limite de vitesse d’acquisition d’image et sa limite de caractérisation des interactions en surface, des études de dynamique moléculaire ou d’éléments sub-surface ne sont pas envisageables. Nous montrons donc que la caractérisation en volume est permise en utilisant une méthode d’imagerie non destructive, la microscopie de champ proche holographique ultrasonore (SNFUH). Cette méthode développée pour étudier à l.air et en liquide, a fourni des informations localisées en profondeur avec une haute résolution spatiale, en utilisant des fréquences de résonance dans la gamme du MHz. Une calibration a été effectuée sur des échantillons de structures enterrées ou non, réalisés par lithographie e-beam. Ces échantillons ont été utilisés pour ajuster les fréquences de résonance et comprendre la formation des images en mode acoustique (profondeur investiguée et inversion de contraste). Cet outil non invasif et innovant de caractérisation a donc été développé. Il présente un énorme potentiel pour des échantillons biologiques en termes de résolution et d’information. Les microscopes AFMclassique et acoustique SNFUH sont soumis à des contraintes de temps. Pour s’en affranchir, un prototype, le microscope à force atomique haute-vitesse (HS-AFM) a été développé par l’équipe du Professeur T. Ando à l’Université de Kanazawa (Japon). Il autorise ainsi le balayage à vitesse vidéo, i.e. 25 images/s, en milieu liquide. Nous avons amélioré le prototype avec une nouvelle génération de boucle d’asservissement et augmenté la zone de caractérisation. La résolution dépend fortement du levier utilisé. De plus une qualité d’image supérieure est obtenue grâce à l’utilisation de surpointes en carbone sur ces mêmes leviers. Finalement, nous montrons des résultats obtenus avec ces deux techniques de microscopies sur différents édi.ces biologiques en milieu liquide. Ainsi, avec le microscope AFM haute-vitesse, des dynamiques biomoléculaires ont pu être visualisées (ex : structures protéine-ADN) avec une résolution nanométrique. Puis une étude des changements conformationnels intracellulaires de kératinocytes vivantes dans leur milieu physiologique a été réalisée par microscopie acoustique SNFUH et montre la dégradation du matériel biologique. L’ensemble de ces résultats ouvre un nouveau champ d’investigation dans le domaine de la biologieThe atomic force microscope (AFM) made part of scanning near-field probe microscopy. Thanks to its versatility, many fields as physics, chemistry or biology use this technique. However, the field of investigation of the classical AFM microscope is limited temporally and spatially. Indeed, due to his scan speed limitation and surface interaction caracterisation limitation, studies of molecular dynamics and sub-surface elements are not possible. We show that the volume caracterisation is permitted using a non-destructive imaging method, called Scanning Near-Field by Ultrasound Holography (SNFUH). This tool developed for study in air and liquid has provided depth information as well as spatial resolution at the nanometer scale using resonant frequencies of about range of MHz. Calibration has been performed on samples of buried or not structures made by e-beam lithography and have been used to adjust the resonant frequency and understand the acoustic image formation (depth investigation and contrast in-version). We have developed a non-invasive and innovative tool of characterization for biology : he presents a huge potential for biological samples in terms of resolution and information. Classical AFM and acoustic SNFUH microscopes are time resolution limited. To overcome this time constraint, a prototype, High Speed Atomic Force Microscope (HS-AFM), has been developed by the team of Prof. T. Ando, Kanazawa University (Japan). It allows a scan rate at video speed, i.e. 25 frames/s, in liquid medium. We have improved the prototype, through a new generation of feedback control and increased the scan area. The resolution depends strongly of the probe used. Moreover a better image quality is obtained through the use of carbon tips on these cantilevers. Finally, we show our results obtained with these two microscopy techniques about biological buildings in liquid environment. Thereby, with the HS-AFM microscope, biomolecular dynamics have been visualized (e.g. protein-DNA structures) with nanometric resolution. Then a study about intracellular conformational changes of keratinocytes living cells in their physiological medium has been realized by acoustic microscopy SNFUH and show deterioration of biological components. All of these results provide new insights in biology field
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Stein, Andrew John 1978. "A metrological atomic force microscope." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/16885.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (p. 245-248).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
This thesis describes the design, fabrication, and testing of a metrological atomic force microscope (AFM). This design serves as a prototype for a similar system that will later be integrated with the Sub-Atomic Measuring Machine (SAMM) under development in collaboration with the University of North Carolina at Charlotte. The microscope uses a piezoelectric tube scanner with a quartz tuning fork proximity sensor to image three-dimensional sample topographies. The probe position is measured with a set of capacitance sensors, aligned so as to minimize Abbe offset error, for direct measurement of probe tip displacements. A PC-based digital control system provides closed-loop control of the lateral scanning and axial height regulation actions of the probe assembly. The lateral scanning system, which dictates the probe's motion in directions parallel to the sample plane, has measured -3 dB closed-loop bandwidths of 189 Hz and 191 Hz in the X and Y directions, respectively. Meanwhile, the axial height regulator, which adjusts the length of the tube scanner to control for a constant gap between the probe tip and the sample surface, has demonstrated a -3 dB closed-loop bandwidth of as high as 184 Hz. The metrological AFM is operational and has been used to collect several images of sample surfaces. Images taken of a silicon calibration grating indicate that the microscope can easily resolve 100 nm-scale step changes in height. However, several errors are observed in the image data. Possible reasons for these errors are discussed, and ideas for follow-on work are suggested.
by Andrew John Stein.
S.M.
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Vithayaveroj, Viriya. "Atomic force microscopy for sorption studies." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-09282004-121825/unrestricted/vithayaveroj%5Fviriya%5F200412%5Fphd.pdf.
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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2005.Dr. Rina Tannenbaum, Committee Member ; Dr. Michael Sacks, Committee Member ; Dr. Sotira Yiacoumi, Committee Chair ; Dr. Costas Tsouris, Committee Co-Chair ; Dr. Ching-Hua Huang, Committee Member. Vita. Includes bibliographical references.
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Grimble, Ralph Ashley. "Atomic force microscopy : atomic resolution imaging and force-distance spectroscopy." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312277.
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Sweetman, Adam. "Forces at the nanoscale : interactions in atomic force microscopy and dielectrophoresis." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11213/.
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Interactions at the nanoscale are governed almost exclusively by electromagnetic forces, but the interplay between different scaling laws produces a vast array of behaviours. We investigate radically different systems spanning almost three orders of magnitude of length scales, and use a variety of experimental techniques to determine the forces present in each regime, and the interplay between them. An important prototypical surface in SPM science has been the Si(100) surface, which due to it’s unstable buckling and complex electronic structure has fostered considerable debate in the surface science community. We have used small amplitude, high sensitivity combined qPlus STM/AFM to investigate tip -- sample interactions on the Si(100) surface at low-temperature in UHV, with a focus on the chemical, and electronic properties of the system and how these are modified by the probe. We present the first atomic resolution combined force/tunnel current results on the surface and show that great care must be taken in interpreting either pure AFM or pure STM data. We also examine tip -- sample interactions on arrays of thiol passivated spin-cast nanoparticles in both UHV and ambient conditions and show for the first time how minor modifications to the experimental parameters can radically alter the data collected, most likely due to the thiol -- surface -- tip interaction. We also present SKPM and voltage spectroscopy of the same samples and show the importance of electrostatic interactions in correct height determination of these network arrays, in parallel with the caution that must be maintained in interpreting CPD data. A key mechanism for the manipulation of meso-scale objects in solution is Dielelectrophoresis, which offers strong material and size specificity and a high degree of spatial control. In the final experimental chapter we investigate the effect of inhomogenous electric fields on nanoparticles in aqueous solution, and reveal how previously uninvestigated electrochemical effects can become important even at high frequencies, and may offer a new and exciting route for the control of self organised nanowires in solution.
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Kong, Jiang-Ti 1975. "Measuring the electrostatic repulsion forces between glycosaminoglycans using the atomic force microscope." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85370.
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McKee, Clayton T. "Investigation of Non-DLVO Forces using an Evanescent Wave Atomic Force Microscope." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28233.
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This dissertation describes new methods for measuring surface forces using evanescent waves, and applications to non-DLVO forces. An evanescent wave, generated at a solid-liquid interface, is scattered by AFM tips or particles attached to AFM cantilevers. The scattering of this wave is used to determine absolute separation between surfaces and/or the refractive index as a function of separation in AFM measurements. This technique is known as evanescent wave atomic force microscopy (EW-AFM). The scattering of an evanescent wave by Si3N4 AFM tips is large and decays exponentially with separation from a refractive index boundary. Thus, scattering is a useful method for measuring the separation between a Si3N4 tip and sample. This method has been used to measure the absolute separation between a tip and sample in the presence of an irreversibly adsorbed polymer film. Measurement of the film thickness and time response of the polymer to applied loads has also been studied. These measurements are not possible using current AFM techniques. In addition to measurements in polymer systems, the simple scattering profile from Si3N4 tips was used to re-examine short range hydration forces between hydrophilic surfaces. Results presented in this thesis suggest this force does not depend on the hydrated radius of the ion between glass and silicon nitride. The scattering generated by a Si3N4 tip has also been used to measure the refractive index of bulk fluids and thin films between hydrophobic surfaces. Based on these results, I have shown that a long-range attraction between hydrophobic surfaces is accompanied by an increase in the refractive index between the tip and surface. From this I have concluded that the attractive force, measured in this study, is the result of an increase in the concentration of organic material between surfaces. Finally, I have shown that the scattering profile depends on the material and size of the scattering object. Scattering from silicon nitride tips is exponential with separation. In contrast, the scattering profile from silicon tips, which are similar in size and geometry, is not a simple exponential. The scattering profile of larger spherical particles attached to cantilevers is also not exponential. It is approximately the sum of two exponentials. The functional form of the scattering profile with separation is consistent with the transmission of evanescent light through flat planar films. This result would suggest that a re-examination of the separation-dependence of scattering in TIRM measurements is necessary.Ph. D.
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Jeong, Younkoo. "HIGH SPEED ATOMIC FORCE MICROSCOPY." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236701109.
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Carnally, Stewart Antoni Michael. "Carbon nanotube atomic force microscopy." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491631.
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This thesis concerns the manufacture of carbon nanotube atomic force microscope (NTAFM) probes and their employment in the high-resolution imaging of biological macromolecules. Attention was focused initially on synthesis of carbon nanotubes and the refinement of the growth processes to obtain nanotubes of controlled dimensions. These growth processes were subsequently used to grow nanotubes directly onto AFM tips, followed by attempts at controlling the dimensions of these directly-grown nanotubes. Individually fabricated NTAFM probes are also described, along with attempts to optimise the strength of the AFM probe-nanotube interaction through the use of various hydrophobic coatings. NTAFM probes produced by both techniques, but predominantly through individually assembled probes using hydrophobic coatings, were used to image a range of natural and synthetic nucleic acid molecules and investigate the influence of the use of a nanotube probe on the dimensions observed.
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Clarke, Richard John. "Hydrodynamics of the atomic force microscope." Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/10649/.
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With a proven ability to uncover fundamental biological processes, the atomic force microscope (AFM) represents one of the most valuable and versatile tools available to the biophysical sciences. We study the unsteady small-scale flows generated within the AFM by its sensing probe (a long thin cantilever), which have received relatively little attention to date, yet which are increasingly relevant in an age of microdevices. The early parts of this thesis investigate some canonical two-dimensional flows driven by oscillations of an infinite-length rigid cantilever. These prove amenable to analysis and enable us to investigate many of the important physical phenomena and compile a comprehensive collection of asymptotic expressions for the drag. The corresponding results lay out the influence of a nearby wall, geometry and oscillation frequency. The limitations of a two-dimensional approach are then explored through the development of a novel unsteady slender-body theory (USBT) for finite-length cylinders, an asymptotic treatment of which offers corrections to traditional resistive-force-theory (RFT) methods by accounting for geometric factors and flow inertia. These ideas are then extended to the study of thin rectangular plates. Two key parameters are identified which promote two-dimensionality in the flow, namely the frequency of oscillation and the proximity of a nearby boundary. We then examine flexible cylinders and plates by coupling the hydrodynamics to linearized elastic beam and plate equations, which simulate the hydrodynamically-damped high-speed deformable motion of the AFM's cantilever, when driven either externally or by Brownian motion. In the latter case, we adopt an approach which offers notable improvements over the most advanced method currently available to the AFM community.
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Anderson, Evan V. "Atomic Force Microscopy: Lateral-Force Calibration and Force-Curve Analysis." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/337.
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This thesis reflects two advances in atomic force microscopy. The first half is a new lateral force calibration procedure, which, in contrast to existing procedures, is independent of sample and cantilever shape, simple, direct, and quick. The second half is a high-throughput method for processing, fitting, and analyzing force curves taken on Pseudomonas aeruginosa bacteria in an effort to inspire better care for statistics and increase measurement precision.
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Muys, James Johan. "Cellular Analysis by Atomic Force Microscopy." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1158.
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Exocytosis is a fundamental cellular process where membrane-bound secretory granules from within the cell fuse with the plasma membrane to form fusion pore openings through which they expel their contents. This mechanism occurs constitutively in all eukaryotic cells and is responsible for the regulation of numerous bodily functions. Despite intensive study on exocytosis the fusion pore is poorly understood. In this research micro-fabrication techniques were integrated with biology to facilitate the study of fusion pores from cells in the anterior pituitary using the atomic force microscope (AFM). In one method cells were chemically fixed to reveal a diverse range of pore morphologies, which were characterised according to generic descriptions and compared to those in literature. The various pore topographies potentially illustrates different fusion mechanisms or artifacts caused from the impact of chemicals and solvents in distorting dynamic cellular events. Studies were performed to investigate changes in fusion pores in response to stimuli along with techniques designed to image membrane topography with nanometre resolution. To circumvent some deficiencies in traditional chemical fixation methodologies, a Bioimprint replication process was designed to create molecular imprints of cells using imprinting and soft moulding techniques with photo and thermal activated elastomers. Motivation for the transfer of cellular ultrastructure was to enable the non-destructive analysis of cells using the AFM while avoiding the need for chemical fixation. Cell replicas produced accurate images of membrane topology and contained certain fusion pore types similar to those in chemically fixed cells. However, replicas were often dehydrated and overall experiments testing stimuli responses were inconclusive. In a preliminary investigation, a soft replication moulding technique using a PDMS-elastomer was tested on human endometrial cancer cells with the aim of highlighting malignant mutations. Finally, a Biochip comprised of a series of interdigitated microelectrodes was used to position single-cells within an array of cavities using positive and negative dielectrophoresis (DEP). Selective sites either between or on the electrode were exposed as cavities designed to trap and incubate pituitary and cancer cells for analysis by atomic force microscopy (AFMy). Results achieved trapping of pituitary and cancer cells within cavities and demonstrated that positive DEP could be used as a force to effectively position living cells. AFM images of replicas created from cells trapped within cavities illustrated the advantage of integrating the Biochip with Bioimprint for cellular analysis.
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Konopinski, D. I. "Forensic applications of atomic force microscopy." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1402411/.
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The first project undertaken was to develop a currently non-existent forensic technique -- data recovery from damaged SIM cards. SIM cards hold data valuable to a forensic investigator within non-volatile EEPROM/flash memory arrays. This data has been proven to be able to withstand temperatures up to 500°C, surviving such scenarios as house fires or criminal evidence disposal. A successful forensically-sound sample extraction, mounting and backside processing methodology was developed to expose the underside of a microcontroller circuit's floating gate transistor tunnel oxide, allowing probing via AFM-based electrical scanning probe techniques. Scanning Kelvin probe microscopy has thus far proved capable of detecting the presence of stored charge within the floating gates beneath the thin tunnel oxide layer, to the point of generating statistical distributions reflecting the threshold voltage states of the transistors. The second project covered the novel forensic application of AFM as a complimentary technique to SEM examination of quartz grain surface textures. The analysis and interpretation of soil/sediment samples can provide indications of their provenance, and enable exclusionary comparisons to be made between samples pertinent to a forensic investigation. Multiple grains from four distinct sample sets were examined with the AFM, and various statistical figures of merit were derived. Canonical discriminant analysis was used to assess the discriminatory abilities of these statistical variables to better characterise the use of AFM results for grain classification. The final functions correctly classified 65.3% of original grouped cases, with the first 3 discriminant functions used in the analysis (Wilks' Lambda=0.336, p=0.000<0.01). This degree of discrimination shows a great deal of promise for the AFM as a quantitative corroborative technique to traditional SEM grain surface examination.
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Acosta, Mejia Juan Camilo. "Atomic force microscopy based micro/nanomanipulation." Paris 6, 2011. http://www.theses.fr/2011PA066691.
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A l’échelle nanoscopique, un problème scientifique fondamental réside dans la difficulté de manipuler de façon interactive et répétable un nano-objet. Cette difficulté est un frein majeur pour des applications comme les nanotransistors, les nanosystèmes ou les futurs NEMS (Nano Electro Mechanical System). Ces dispositifs émergents sont ainsi ralentis dans leur cadre expérimental. Cette thèse s’inscrit dans la continuité des recherches développées au sein de l’équipe de microrobotique de l'ISIR. Elle se focalise sur l'exploitation de capteurs d'effort pour la manipulation contrôlée à plusieurs doigts actifs. Le microscope à force atomique est utilisé pour ses propriétés de capteur d'effort. Dans un premier temps, un préhenseur composé de deux doigts indépendants avec mesures des forces d'interaction a été conçue. Avec ce système original, des micromanipulations en trois dimensions de microsphères ont été réalisée avec succès dans l'air, en mesurant de façon continue les efforts d'interaction. Ce système a aussi été utilisé pour saisir et déposer des nanofils afin de former des nanocroix, ces dernières étant des nanostructures émergentes pour la fabrication, par jonctions, de nanotransistors. Par la suite, des oscillateurs en quartz ont été utilisés pour la caractérisation de nanostructures, avec retour d'effort dynamique. Le comportement non-linéaire en raideur de nanohélices lors de l'élongation a été caractérisé pour la première fois sur la totalité de la plage. Enfin, des sondes en quartz de haute fréquence ont été exploitées pour augmenter la vitesse d'acquisition d'images de l'AFM. De cette manière, la tâche de manipulation et d'imagerie en parallèle sous AFM a été optimisée et de nombreuses applications sont maintenant envisagées
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Sykulska-Lawrence, Hanna Maria. "Atomic force microscopy for Martian investigations." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4396.
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The Phoenix Mars Lander includes a Microscopy, Electrochemistry and Conductivity Analyser (MECA) instrument for the study of dust and regolith at the Martian arctic. The microscopy payload comprises an AFM and Optical Microscope (OM) to which samples are delivered by a robot arm. The setup allows imaging of individual dust and soil particles at a higher spatial resolution than any other in-situ instrument. A fully functioning test-bed of the flight microscopy setup within an environmental chamber to simulate Mars conditions was assembled at Imperial College, enabling characterization of the microscopes. Samples are collected on small disks rotated to the vertical position for imaging, with each substrate surface promoting different adhesion mechanisms. The vertical mounting necessitates good adhesion of particles to substrates. Moreover, to achieve safe operation and good AFM scans, a sparse field of particles is required. This work investigates models and experimental setups which consider the adhesion mechanisms of particles, including under Mars conditions. These models incorporate the forces from the AFM cantilever during scanning, particle-substrate adhesion and particle-tip adhesion. The solution offered to the problem of unstable particles is substrates with engineered features, micromachined in silicon, to trap and stabilise particles for AFM and reduce the loading of the sample to a suitable level. Various designs were investigated in a series of tests, and a final design was created for a substrate for AFM during the mission. The substrates were fabricated and incorporated on the sample wheel on Phoenix, now on Mars. The MECA results are discussed, focusing in particular on the characterization, calibration and cataloguing of samples using the Imperial College testbed. The best ways of obtaining data from the setup were investigated. These strategies were used during the Phoenix mission. Finally, the extant microscopy data acquired during surface operations are presented and the overall operations procedures discussed.
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Kesner, Samuel B. (Samuel Benjamin). "Tip steering of the Atomic Force Microscope." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36755.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 58-59).
The Atomic Force Microscope (AFM) is a powerful tool for the imaging of extremely small objects on the scale of nanometers, like carbon nanotubes and strands of DNA. There currently is a need for methods to actively steer the probe tip of the AFM in order to greatly reduce the time required to image certain samples. This paper proposes a tip steering method that utilizes the vertical feedback information from the AFM sensor as well as the dimensions of the sample object to determine and maintain a scanning trajectory. A comparison of similar trajectory tracking methods is also presented. The AFM system and operation is discussed in order to justify the tip steering method. Finally, the method proposed is successfully simulated with a DNA strand sample in the presence of measurement noise.
S.B.
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Lantz, Mark Alfred. "Tribological studies with the atomic force microscope." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627159.
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Moore, Sean O'Neill. "QUANTIFYING THE BIOMECHANICAL FORCES BETWEEN PROTEINS INVOLVED IN ELASTIN SYNTHESIS USING ATOMIC FORCE MICROSCOPY." Cleveland State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=csu1546450170942598.
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Cisneros, Armas David Alejandro. "Molecular assemblies observed by atomic force microscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1182777560689-53566.
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We use time-lapse AFM to visualize collagen fibrils self-assembly. A solution of acid-solubilized collagen was injected into the AFM fluid cell and fibril formation was observed in vitro. Single fibrils continuously grew and fused with each other until the supporting surface was completely covered by a nanoscopically well-defined collagen matrix. Laterally, the fibrils grew in steps of ~4 nm suggesting a two-step mechanism. In a first step, collagen molecules associated together. In the second step, these molecules rearranged into a structure called a microfibril. High-resolution AFM topographs revealed substructural details of the D-band architecture. These substructures correlated well with those revealed from positively stained collagen fibers imaged by transmission electron microscopy. Secondly, a covalent assembly approach to prepare membrane protein for AFM imaging that avoids crystallization was proposed. High-resolution AFM topographs can reveal structural details of single membrane proteins but, as a prerequisite, the proteins must be adsorbed to atomically flat mica and densely packed in a membrane to restrict their lateral mobility. Atomically flat gold, engineered proteins, and chemically modified lipids were combined to rapidly assemble immobile and fully oriented samples. The resulting AFM topographs of single membrane proteins were used to create averaged structures with a resolution approaching that of 2D crystals. Finally, the contribution of specific amino acid residues to the stability of membrane proteins was studied. Two structurally similar proteins sharing only 30% sequence identity were compared. Single-molecule atomic force microscopy and spectroscopy was used to detect molecular interactions stabilizing halorhodopsin (HR) and bacteriorhodopsin (BR). Their unfolding pathways and polypeptide regions that established stable segments were compared. Both proteins unfolded exactly via the same intermediates. This 3 Molecular Assemblies observed by AFM observation implies that these stabilizing regions result from comprehensive contacts of all amino acids within them and that different amino acid compositions can establish structurally indistinguishable energetic barriers. However, one additional unfolding barrier located in a short segment of helix E was detected for HR. This barrier correlated with a Pi-bulk interaction, which locally disrupts helix E and divides into two stable segments.
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Spitzner, Eike-Christian. "Subsurface and MUSIC-Mode Atomic Force Microscopy." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-94864.
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Ziel dieser Arbeit war die Entwicklung neuer Methoden in der Rasterkraftmikroskopie, um die Qualität und Interpretierbarkeit von Oberflächenabbildungen auf der Nanometerskala, vor allem jener sehr weicher Proben, entscheidend zu verbessern. Der für polymere und biologische Materialien standardmäßig verwendete intermittierende Kontaktmodus führt auf weichen Oberflächen zu verfälschten Abbildungen der Topographie und der mechanischen Eigenschaften. In dieser Arbeit wurden Techniken entwickelt, die einerseits zerstörungsfreie, tiefenaufgelöste Rasterkraftmikroskopie und andererseits Einzelmessungen mit variabler Dämpfung im intermittierenden Kontaktmodus ermöglichen. Die laterale Auflösung beider Methoden liegt dabei im Rahmen herkömmlicher Techniken (< 10 nm). Die Tiefenauflösung konnte im Vergleich zu anderen Methoden um eine Größenordnung auf unter 1 nm verbessert werden. Die neuen Methoden wurden auf einer breiten Palette polymerer Materialien angewandt. Die räumliche Struktur oberflächennaher Bereiche eines Blockcopolymerfilms konnte im Vergleich zu herkömmlichen Methoden deutlich genauer abgebildet werden. Gleiches wurde auf elastomerem Polypropylen erreicht. Es konnten weiche, amorphe Deckschichten auf teilkristallinen Polymeren nachgewiesen und vermessen werden, was in der organischen Elektronik eine wichtige Rolle spielen kann. Die innere Struktur selbstangeordneter Nanodrähte aus Oligothiophen-Aggregaten konnte aufgelöst werden und es wurde die Selbstanordnung von Kollagenfibrillen im gequollenen Zustand beobachtet.
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Smith, Benjamin A. "Cellular biomechanics investigated by atomic force microscopy." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85648.
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Living biological cells are highly complex, multifunctional systems whose physical attributes are relatively unknown. Critical functions involving plasticity of cell morphology, connectivity and response to stimuli are proposed to be fundamentally related to the micromechanical character and the ability of the cell to exert directed mechanical signaling. Unique abilities of atomic force microscopy in measuring cellular viscoelastic properties (on length scales from nanometers to microns) are explored with specific applications to (1) airway smooth muscle cells and (2) hippocampal neurons. Surface indentation techniques for stiffness mapping, as well as quantitative measurements of frequency-dependent complex rheology are featured. Structural and molecular determinants of dynamic mechanical behavior are identified. In smooth muscle cells, an isotropic fiber network provides strong resistance to deformation. Actin polymerization is largely responsible for stiffening following contractile activation, not myosin cross-bridge formation as expected. On neuronal dendrites, stiffness contrast correlates with known distributions and stability of cytoskeletal elements: microtubules along the shafts and dynamic actin in the spines (micron-sized surface protrusions). Focus is given to dendritic spines as the post-synaptic contact sites for most excitatory transmission between neurons. Large heterogeneity is observed in spine mechanical properties, but stiffer spines appear to be associated with axon-like contacts. Spines may stiffen in response to synaptic stimulation, in agreement with recent observations of actin-based stabilization of spine shape (reduced motility) following excitatory treatments.Remarkably, the frequency dependence of the complex shear moduli (0.5-100 Hz indentations) of both cellular systems is described well by the same rheological model: that of soft glassy materials existing just above the glass transition. The central feature of this model is that storage ( G') and loss moduli (G") scale in parallel as a weak power-law function of frequency. Power-law exponents (alpha), measured to be of the order 0.1, are related to the level of molecular agitations in the cell and determine the degree of solid-like (G' >> G" with a glass transition at alpha = 0) or fluid-like behavior (G' << G" with alpha = 1 for a pure fluid). The soft glassy hypothesis is founded on the concepts of disorder and metastability of structural elements. A Newtonian viscosity (pure fluid) component is also identified with significant effects for high frequency deformations. Together these properties are critical for describing cellular remodeling: contraction in smooth muscle cells or synaptic plasticity at dendritic spines.
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Markiewicz, Peter C. "Atomic force microscopy studies of mesoscopic structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq35239.pdf.
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Jarvis, Suzanne Philippa. "Atomic force microscopy and tip-surface interactions." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359441.
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Cassidy, A. M. C. "Probing pharmaceutical materials using atomic force microscopy." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597359.
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Microscopic techniques were used to study the surface behaviour of model active pharmaceutical ingredients (APIs) and excipients, while under stress, and this was compared with the response of the bulk material. The model APIs were caffeine/oxalic acid, caffeine/malonic acid cocrystals and aspirin whilst spheronised microcrystalline cellulose (s-MCC), pregelatinised starch (PGS) and dicalcium phosphate dehydrate served as examples of excipients. The difference between the surface and bulk behaviour of caffeine cocrystals in response to storage in controlled humidity environments was investigated. Surface imaging illustrated an anisotropic element to the microstructure of the caffeine cocrystals, which became more pronounced at the extremities of relative humidity (RH) storage. The trends in surface reactivity which were observed for the cocrystals were found to follow those previously reported for bulk behaviour, using PXRD. Atomic force microscopy imaging, however, gave an earlier indication of incompatibility between the ecocrystals and > 75% RH, with surface transformations occurring on a shorter timescale than indicated from the results of bulk analysis. This work represents the first reported analysis of organic molecular cocrystals by AFM. The material properties and subsurface structure of s-MCC and PGS were examined using AFM. Phase imaging and force measurements identified heterogeneity in the material properties of these excipient particles. In the case of s-MCC, the results were used to support a theory for intragranular porosity. The solid-state hydrolysis of aspirin crystals in the presence of dicalcium phosphate dehydrate was studied, using in situ AFM techniques.
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Sapcharoenkun, Chaweewan. "Controlled nanostructure fabrication using atomic force microscopy." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7593.
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Scanning probe microscopy (SPM) nanolithography has been found to be a powerful and low-cost approach for sub-100 nm patterning. In this thesis, the possibility of using a state-of-the-art SPM system to controllably deposit nanoparticles on patterned Si substrates with high positional control has been explored. These nanoparticles have a range of interesting properties and have been characterised by electron microscopy and scanning probe microscopy. The influence of different deposition parameters on the nanoparticle properties was studied. Contact mode atomic force microscopy (AFM)-based local oxidation nanolithography (LON) was used to oxidise sample surfaces. Two different substrates were studied which were native oxide silicon (Si) and molybdenum (Mo). A number of factors that influence the height and width of the oxide features were investigated in order to achieve the optimal oxidation efficiency. The height and width of the oxide structures were found to be strongly dependent on the applied voltage and scan speed. The tunneling AFM (TUNA) technique was used to measure the ultralow currents flowing between the tip and the sample during the oxidation process. It was found that a threshold voltage for our oxidation experiments was -4.0 ± 1.6 V applied to the tip when fabricating geometric patterns as well as 2.9 ± 1.6 V and 2.8 ± 2.2 V applied to the substrate for nanodot fabrication. In addition, comparisons of nanodot-array patterns produced with different AFM tips were studied. The influence of applied voltage, type of AFM tip and substrate, humidity and ramping time has been studied for dot formation providing a comparison between native oxide Si and Mo surfaces. The nanodot sizes were found to be clearly dependent on the applied voltage, type of substrate, relative humidity and ramping time. Dip-pen nanolithography (DPN) was used to study a direct deposition strategy for gold (Au) nanodot fabrication on a native oxide Si substrate. In this process, hydrogen tetrachloroaurate (HAuCl4) molecules were deposited onto the substrate via a molecular diffusion process, in the absence of electrochemical reactions. This approach allowed for the generation of Au dots on the SiO2 substrate without the need for surface modification or additional electrode structures. The dependence of the size of the Au dots on different „scanning coating‟ (SC) times of AFM tips was studied. A thermal annealing process was used to decompose the generated HAuCl4 molecular dots to leave Au (0) metal dots. A stereomicroscope has been used for preliminary observation of different steps of Au deposition treatments. A scanning electron microscope (SEM) was used to characterise the SC AFM tips both before and after the DPN process. SEM energy-dispersive X-ray spectroscopy (EDS) has provided information about the elemental content of deposited particles for different annealing temperatures. Fountain-pen nanolithography (FPN) has also been used to study nanowriting of HAuCl4 salt and a variety of solvents on a native oxide Si surface. In this technique, a nanopipette was mounted within an AFM to deliver appropriate solutions to the silica substrate. We found that an aqueous Au salt solution was the most suitable ink for depositing gold using the FPN technique. In the case of solvents alone, ethanol and toluene were achieved with depositing onto a SiO2 substrate using the FPN technique.
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Baker, Andrew Arthur. "High resolution atomic force microscopy of polysaccharides." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264076.
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Dudda, Bruna. "Morphology of leds by atomic force microscopy." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6647/.
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The concern of this work is to present the characterization of blue emitting GaN-based LED structures by means of Atomic Force Microscopy. Here we show a comparison among the samples with different dislocation densities, in order to understand how the dislocations can affect the surface morphology. First of all we have described the current state of art of the LEDs in the present market. Thereafterwards we have mentioned in detail about the growth technique of LED structures and the methodology of the characterization employed in our thesis. Finally, we have presented the details of the results obtained on our samples studied, followed by discussions and conclusions.
L'obiettivo di questa tesi é quello di presentare la caratterizzazione mediante Microscopia a Forza Atomica di strutture di LED a emissione di luce blu a base di nitruro di gallio (GaN). Viene presentato un confronto tra campioni con differente densità di dislocazioni, allo scopo di comprendere in che modo la presenza di dislocazioni influisce sulla morfologia della superficie. Innanzitutto, viene descritto il presente stato dell'arte dei LED. Successivamente, sono forniti i dettagli riguardanti la tecnica di crescita delle strutture dei LED e il metodo di caratterizzazione adottato. Infine, vengono mostrati e discussi i risultati ottenuti dallo studio dei campioni, seguiti dalle conclusioni.
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Sun, Mingzhai. "Cell mechanics studied using atomic force microscopy." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5499.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on June 17, 2009) Vita. Includes bibliographical references.
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Mazzeo, Aaron D. (Aaron David) 1979. "Accurate capacitive metrology for atomic force microscopy." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33912.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 219-224).
This thesis presents accurate capacitive sensing metrology designed for a prototype atomic force microscope (AFM) originally developed in the MIT Precision Motion Control Lab. The capacitive measurements use a set of commercial capacitance sensors intended primarily for use against a flat target. In our design, the capacitance sensors are used with a spherical target in order to be insensitive to target rotations. The moving AFM probe tip is located approximately at the center of the spherical target to make the capacitive sensing insensitive to the probe tip assembly's undesirable rotation on the order of 3 x 10⁻⁴ rad for 10 [mu]m of lateral travel [48]. To accurately measure displacement of the spherical target relative to the capacitance sensors, models for the capacitance between a sphere and a circular disc were developed with the assistance of Katherine Lilienkamp. One of the resulting non-linear models was combined with the appropriate kinematic transformations to accurately perform measurement scans on a 20 [mu]m x 20 [mu]m surface with step heights of 26.5 nm. The probe tip positions during these scans were also calculated in real- time using Lilienkamp's non-linear capacitance model with a set of transformations and 3-D interpolation techniques implemented at 10 kHz. The scans were performed both in tapping and shear detection modes.
(cont.) Localized accuracy on the order of 1 nm with RMS noise of approximately 3 nm was attained in measuring the step heights. Surface tracking control and speed were also improved relative to an earlier prototype. Lateral speeds of approximately 0.8 [mu]m/s were attained in the tapping mode. In addition to improving the original prototype AFM's scan speed and ability to attain dimensional accuracy, a process for mounting an optical fiber probe tip to a quartz tuning fork was developed. This mounting process uses Post-it notes. These resulting probe-tip/tuning-fork assemblies were tested in both the tapping and shear modes. The tests in the tapping mode used the magnitude of the fork current for accurate surface tracking. The tests performed in the shear mode used the magnitude and phase of the fork current for accurate surface tracking.
by Aaron David Mazzeo.
S.M.
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Yeo, Yee 1977. "Image processing for precision atomic force microscopy." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88854.
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Vicary, James Alexander. "High-speed atomic force microscopy for nanofabrication." Thesis, University of Bristol, 2006. http://hdl.handle.net/1983/b79a500e-8856-470f-a3aa-bde7f531cb0a.
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Sobek, Joanna Amanda. "Atomic force microscopy studies of potassium channels." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669955.
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Li, Changyi. "Cryogenic atomic force microscope for characterization of nanostructures." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2727.
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Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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LEMOS, FELIPE PTAK. "QUARTZ CRYSTAL OSCILLATORS AS ATOMIC FORCE MICROSCOPE SENSORS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=27637@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
BOLSA NOTA 10
A caracterização de cristais osciladores de quartzo (QTF) foi realizada nesta dissertação com o objetivo de implementá–los como sensores de um microscópio de força atômica (AFM). O QTF possui várias vantagens em relação aos cantilevers tradicionais de silício. Utilizado em modos dinâmicos de operação do AFM, o QTF possui maior fator de qualidade e rigidez, permitindo melhor sensibilidade em força e o uso de baixas amplitudes de oscilação para imageamento do que cantilevers tradicionais. Nesse trabalho, parâmetros mecânicos e elétricos do QTF foram medidos. Além disto, um estudo da influência da adição de massa nos braços do QTF foi realizado. Para a implementação do QTF no AFM, um sistema de feedback composto de um amplificador lock–in e um amplificador diferencial foi desenvolvido e testado. Adicionalmente, um novo cabeçote para o microscópio foi desenvolvido para adaptar o QTF ao microscópio.
The characterization of quartz tuning forks (QTF) was performed in this dissertation, aiming to implement them as sensors at an atomic force microscope (AFM). The QTF has several advantages over traditional silicon cantilevers. Used in dynamic AFM modes, the QTF has higher quality factor and stiffness, allowing better force sensitivity and lower amplitudes of oscillation for imaging than traditional cantilevers. In this work, electrical and mechanical parameters of the QTF were obtained. Furthermore, a study of the influence of additional mass on the QTF prongs was performed. To implement the QTF at the AFM, a feedback system composed of a lock–in amplifier and a differential amplifier was developed and tested. Additionally, a new microscope head was designed to adapt the QTF to the microscope.
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Lim, Kwang Yong S. M. Massachusetts Institute of Technology. "Optical system for high-speed Atomic Force Microscope." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61912.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 191-192).
This thesis presents the design and development of an optical cantilever deflection sensor for a high speed Atomic Force Microscope (AFM). This optical sensing system is able to track a small cantilever while the X-Y scanner moves in the X-Y plane at 1KHz over a large range of 50x50 microns. To achieve these requirements, we evaluated a number of design concepts among which the lever method and the fiber collimator method were selected. Experiments were performed to characterize the performance of the integrated AFM and to show that the cantilever tracking while the scanner is in operation was accomplished. A triangular grating was imaged with the lever method optical subassembly integrated with the scanner to demonstrate the effectiveness of the approach.
by Kwang Yong Lim.
S.M.
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Houck, Andrew Careaga. "A modular atomic force microscope for nanotechnology research." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100129.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 91-97).
The atomic force microscope (AFM) has become an essential tool in a wide range of fields, from materials science and semiconductor research to molecular biology. Various research efforts have enhanced the capabilities of this powerful instrument, which has enabled new insights into nanoscale phenomena. Despite decades of research, state-of-the-art AFMs are not widely utilized. In order to accelerate the proliferation and development of these instruments, a modular atomic force microscope is presented. The optical, mechanical, and instrumentation components of the AFM can all be easily exchanged. The instrument can be reconfigured for fundamentally different imaging tasks and can be used as a platform for continued research efforts. The optical beam deflection (OBD) setup can be configured for coaxial or off-axis detection for use with cantilevers of any size. A simple and low-cost design is presented, and an AFM is implemented based on the design. The instrument is tested in two different imaging configurations. First, a configuration for high-speed imaging with small cantilevers is used to image copper deposition on gold in contact mode in liquid. Second, a configuration for large cantilevers is used to visualize the mechanical properties of a polymer blend in tapping mode in air. The flexibility of the modular instrument is leveraged to develop a new capability for high-speed AFM. Multi-actuated and dual-actuated sample scanners have enhanced the high-speed performance of AFMs by combining multiple nanopositioners with different range and bandwidth characteristics. While this and other improvements have made AFM scanners effective for high-speed imaging, out-of-plane sensing has not been developed adequately. Out-of-plane sensing enhances the capability for quantitative in situ analysis by measuring changes in sample thickness during dynamic processes. This is especially useful in materials science and electrochemical applications, in which understanding of changes in bulk sample thickness is essential. A sensing methodology for high-speed dual-actuated out-of-plane positioning is presented. A silicon-type strain gauge is used to measure the displacement of the low frequency nanopositioner. A piezoelectric sensor is used to measure high-frequency displacement. The sensor is incorporated into a novel diaphragm flexure nanopositioner with annular piezoelectric actuator. Fusion of the two sensors for high-speed imaging tasks is discussed. Performance of the two sensors is evaluated, and further developments to integrate the sensing methodology into the modular atomic force microscope are discussed. Finally, the modular AFM is used in two dynamic nanoscale imaging tasks. High speed atomic force microscopy has enabled many novel discoveries across a range of applications, especially in biological fields. However, applications in materials science and electrochemistry have not been as thoroughly explored. First, electrochemical deposition of copper on gold during cyclic voltammetry (CV) trials is studied. Electrochemical data from a potentiostat during the CV trials collected in parallel with the AFM images to enrich the analysis. The effect of different initial surface conditions on deposition and stripping is observed. Second, calcite dissolution in low-pH environments is imaged. Dissolution processes in sulfuric and hydrochloric acid solutions are compared. It is apparent that the rhombohedral crystalline structure of the calcite clearly influences the dissolution kinetics in both cases. Erosion of thick calcite terraces is observed in both solutions. However, differences in the dissolution kinetics suggest that the anions play an important role in the process. Multi-actuated sample scanners are particularly well-suited for these two applications, as they involve rapid changes in features at the nanometer scale (e.g. calcite monolayer etch pits and copper nucleation sites) as well as the micron scale (e.g. calcite terraces and copper grains).
by Andrew Careaga Houck.
S.M.
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Nemutudi, Rudzani. "Mesoscopic devices fabricated using an atomic force microscope." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620316.
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Clark, Spencer C. "Development of the Evanescent Wave Atomic Force Microscope." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29704.
Full textAbstract:
The conventional atomic force microscope (AFM) is equipped with a single optical detection system. Probe-sample separation is determined in an independent deflection with respect to AFM z-translation experiment. This method of determining probe-surface separation is relative, susceptible to drift and does not provide real time separation information. The evanescent wave atomic force microscope (EW-AFM) utilizes a second, independent detection system to determine absolute probe-surface separation in real time. The EW-AFM can simultaneously acquire real-time force and probe-sample separation information using the optical lever and evanescent scattering detection systems, respectively. The EW-AFM may be configured with feedback on the optical-lever system for constant force applications or with feedback on evanescent wave scattering intensity for constant height applications.
Scattering of the evanescent wave exponential decay profile is used to determine probe-surface separation. Sub-micron sized dielectric and metallic probes show exponential scattering profiles, micron sized polystyrene and borosilicate microspheres show non-exponential profiles when they are affixed beneath the cantilever tip. By affixing the microspheres to the end of the AFM cantilever exponential and non-exponential profiles were observed.
The EW-AFM can be used to conduct force-distance and imaging experiments. The EW-AFM was used to measure the thickness of surfactant bilayers formed at the silica-solution interface using silicon nitride AFM tips. The presence of a refractive index difference between the surfactant bilayer and the solution does not influence the accuracy of the surfactant bilayer thickness measurement. The EW-AFM was used to scan a 2 x 2 micron area in constant height mode. The probe was brought to within 6 nanometers of a planar dielectric surface using the evanescent wave intensity as a height reference with accuracy of ± 1 nm. This capability may be utilized to observe charge heterogeneity at the solid-liquid interface with nanometer lateral resolution or to map chemical functional group heterogeneity based on perturbations to the electrical double layer.
The EW-AFM evanescent scattering system has an absolute separation resolution of 0.3 nm compared to 1.0 nm relative separation resolution for the optical lever system. In constant scattering (constant height) mode the real time separation precision is about 2 nm.Ph. D.
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McBride, Sean P. "Surface science experiments involving the atomic force microscope." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/13459.
Full textAbstract:
Doctor of PhilosophyDepartment of Physics
Bruce M. Law
Three diverse first author surfaces science experiments conducted by Sean P. McBride 1-3 will be discussed in detail and supplemented by secondary co-author projects by Sean P. McBride, 4-7 all of which rely heavily on the use of an atomic force microscope (AFM). First, the slip length parameter, b of liquids is investigated using colloidal probe AFM. The slip length describes how easily a fluid flows over an interface. The slip length, with its exact origin unknown and dependencies not overwhelming decided upon by the scientific community, remains a controversial topic. Colloidal probe AFM uses a spherical probe attached to a standard AFM imaging tip driven through a liquid. With the force on this colloidal AFM probe known, and using the simplest homologous series of test liquids, many of the suspected causes and dependencies of the slip length demonstrated in the literature can be suppressed or eliminated. This leaves the measurable trends in the slip length attributed only to the systematically varying physical properties of the different liquids. When conducting these experiments, it was realized that the spring constant, k, of the system depends upon the cantilever geometry of the experiment and therefore should be measured in-situ. This means that the k calibration needs to be performed in the same viscous liquid in which the slip experiments are performed. Current in-situ calibrations in viscous fluids are very limited, thus a new in-situ k calibration method was developed for use in viscous fluids. This new method is based upon the residuals, namely, the difference between experimental force-distance data and Vinogradova slip theory. Next, the AFM’s ability to acquire accurate sub nanometer height profiles of structures on interfaces was used to develop a novel experimental technique to measure the line tension parameter, τ, of isolated nanoparticles at the three phase interface in a solid-liquid-vapor system. The τ parameter is a result of excess energy caused by the imbalance of the complex intermolecular forces experienced at the three phase contact line. Many differences in the sign and magnitude of the τ parameter exist in the current literature, resulting in τ being a controversial topic.
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Razatos, Anneta Panagis. "Factors and forces involved in the initial events of bacterial adhesion as monitored by atomic force microscopy /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Mattocks, Philip. "Scanning tunnelling microscopy and atomic force microscopy of semiconducting materials." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/scanning-tunnelling-microscopy-and-atomic-force-microscopy-of-semiconducting-materials(9bc10301-2c4d-4dfb-a374-f65ee37ae23a).html.
Full textAbstract:
Michael Faraday first documented semiconducting behaviour in 1833 whenhe observed that the resistance of silver sulphide decreased with temperature,contrary to the behaviour of normal conducting materials. Up untilthe middle of the twentieth century, semiconductors were used as photodetectors,thermisters and rectifiers. In 1947 the invention of the transistor byBardeen and Brattain lead to the integrated circuit and paved the way formodern electronics. The need to produce smaller and faster transistors hasdriven research into new semiconductors. This thesis will first introduce the physics of semiconductors, followed bya description of the experimental techniques employed; scanning tunnellingmicroscopy (STM) and atomic force microscopy (AFM). Chapter 3 is concernedwith explaining anomalous scanning tunnelling spectroscopy resultsobtained for Si(100) and GaAs(110). To this end, a one-dimensional planarmodel, in which surface states affect the charge distribution and tunnellingin the system is proposed. Graphene, a novel two-dimensional material,is introduced in Chapter 4. Scanning tunnelling microscopy measurementsof graphene suspended on a metal grid are presented in this chapter. Finally,Indium antimonide Schottky contacts are investigated using conductingatomic force microscopy in Chapter 5.