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1
Cooper, Katherine. "AFM and C-AFM Studies of GaN Films". VCU Scholars Compass, 2005. http://scholarscompass.vcu.edu/etd/1246.
Testo completoAbstract (sommario):
This thesis uses the techniques of atomic force microscope (AFM) and conductive AFM (C-AFM) to study the conduction properties of n-type GaN films. A total of 16 samples were examined and grouped according to their surface morphologies and conduction behaviors. The most common type of surface morpliology was that of Ga-rich samples having undulating "hillocks" with interspersed holes. Although most of the samples had this common morphology, their local conduction behaviors were not all similar. Local I-V spectra of the tip-sample Schottky contact could be grouped according to three major types: low leakage, high leakage, and "p-type". The highest quality samples with low leakage were usually grown at moderate temperatures (~650°C). For such samples, localized leakage only occurred at screw dislocations located at small pits terminating surface hillocks. I-V spectra taken on and off such hillocks were fit in forward bias to determine whether field emission or Frenkel-Poole conduction were dominant. Although field emission is a good fit compared to Frenkel-Poole, yielding reasonable values for the barrier height, the results are not yet conclusive without variable temperature studies.
2
Rossell, Jacqueline. "Protein immobilisation for AFM". Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404144.
Testo completo
3
Lee, Sunyoung S. M. Massachusetts Institute of Technology. "Chemical functionalization of AFM cantilevers". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34205.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references (p. 47-52).
Atomic force microscopy (AFM) has been a powerful instrument that provides nanoscale imaging of surface features, mainly of rigid metal or ceramic surfaces that can be insulators as well as conductors. Since it has been demonstrated that AFM could be used in aqueous environment such as in water or various buffers from which physiological condition can be maintained, the scope of the application of this imaging technique has been expanded to soft biological materials. In addition, the main usage of AFM has been to image the material and provide the shape of surface, which has also been diversified to molecular-recognition imaging - functional force imaging through force spectroscopy and modification of AFM cantilevers. By immobilizing of certain molecules at the end of AFM cantilever, specific molecules or functionalities can be detected by the combination of intrinsic feature of AFM and chemical modification technique of AFM cantilever. The surface molecule that is complementary to the molecule at the end of AFM probe can be investigated via specificity of molecule-molecule interaction.
(cont.) Thus, this AFM cantilever chemistry, or chemical functionalization of AFM cantilever for the purpose of chemomechanical surface characterization, can be considered as an infinite source of applications important to understanding biological materials and material interactions. This thesis is mainly focused on three parts: (1) AFM cantilever chemistry that introduces specific protocols in details such as adsorption method, gold chemistry, and silicon nitride cantilever modification; (2) validation of cantilever chemistry such as X-ray photoelectron spectroscopy (XPS), AFM blocking experiment, and fluorescence microscopy, through which various AFM cantilever chemistry is verified; and (3) application of cantilever chemistry, especially toward the potential of force spectroscopy and the imaging of biological material surfaces.
by Sunyoung Lee.
S.M.
4
Subedi, Laxmi P. "AFM Tip-Graphene-Surface Interactions". University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1291144388.
Testo completo
5
Hegrová, Veronika. "Aplikace korelativní AFM/SEM mikroskopie". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-402580.
Testo completoAbstract (sommario):
This thesis is dealing with application of Correlative Probe and Electron Microscopy. All measurements were carried out by atomic force microscope LiteScope which is designed especially to be combined with electron microscopes. Advantages of Correlative AFM/SEM Microscopy are demonstrated on selected samples from field of nanotechnology and material science. Application of the correlative imaging was proposed and then realized particularly in case of low-dimensional structures and thin films. Further, this thesis deals with the possibility of combining Correlative AFM/SEM Microscopy with other integrated techniques of an electron microscope such as Focused Ion Beam and Energy Dispersive X-rays Spectroscopy.
6
Andersen, Christopher. "The construction of carbon nanotube AFM probes for high resolution AFM of novel biological systems". Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421480.
Testo completo
7
Sonnenberg, Lars. "AFM-basierte Desorption einzelner oberflächenadsorbierter Polyelektrolyte". Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-76109.
Testo completo
8
Filip-Boar, Diana. "AFM-CSLM microrheology of aggregated emulsions". Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/56171.
Testo completo
9
Gröger, Roland. "Nanokontaktdrucken mit AFM-gesteuert phasenseparierten Blockcopolymerschichten". Karlsruhe Forschungszentrum Karlsruhe, 2006. http://d-nb.info/986521612/34.
Testo completo
10
FILHO, HENRIQUE DUARTE DA FONSECA. "METALLIC NANOSTRUCTURE FABRICATION BY AFM LITHOGRAPHY". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6061@1.
Testo completoAbstract (sommario):
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORNesta dissertação de mestrado, nós desenvolvemos um processo de litografia baseado na técnica de microscopia de força atômica. O estudo do processo de litografia aqui utilizado inicia-se com a deposição e caracterização de filmes finos de sulfeto de arsênio amorfo (a-As2S3) em substratos de silício e a deposição de uma camada metálica de alumínio, utilizada como máscara, sobre a superfície do a-As2S3. O microscópio de força atômica é utilizado para escrever os padrões de forma controlada na camada metálica, e para tal, a influencia dos parâmetros de controle do microscópio na realização da litografia foi analisada. Para a transferência do padrão litografado realiza-se um posterior processo de fotossensibilização e dissolução química do a-As2S3 com uma solução de K2CO3. Após a dissolução, uma camada de ouro foi depositada por erosão catódica DC, seguido de uma nova dissolução, desta vez com NaOH resultando na transferência de nanoestruturas de Au para o substrato de silício.
In this dissertation, we have developed a lithography process based on the atomic force microscopy of technique. The study of the lithography process starts with the deposition and characterization of amorphous arsenic sulfide thin films (a-As2S3) in silicon substrates and the deposition of a metallic aluminum layer, used as mask, on the surface of the a-As2S3. An atomic force microscope was used to write patterns in a controlled way on the metallic layer. Therefore, the influence of microscope feedback system on the accomplishment of the lithography was analyzed. In order to transfer the lithographed pattern to a silicon substrate, the a- As2S3 was exposed to a UV light source and was dissolved with a K2CO3 solution. Then, a thin gold layer was deposited by sputtering DC, and a new dissolution, now with NaOH was performed, leading to the deposition of Au nanostructures onto the silicon substrate.
11
Podgaynyy, Nikolay [Verfasser]. "AFM-Untersuchungen auf Elektrodenoberflächen / Nikolay Podgaynyy". Bonn : Universitäts- und Landesbibliothek Bonn, 2013. http://d-nb.info/1044971282/34.
Testo completo
12
Rudnicki, Kamil. "MOSFET transistor fabrication on AFM tip". Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5398/.
Testo completoAbstract (sommario):
The project is concerned with the development of methods for the fabrication of magnetic sensor devices on Atomic Force Microscopy (AFM) probes and their characterization. The devices use the principle of the Hall effect (based on the Lorentz force) to sense the magnetic properties of a magnetized specimen. In the past Hall bar sensors have been fabricated using semimetals such as Bismuth, or using 2-d electron gas material based on heterojunctions in III-V material. The former probes are limited by low sensitivity. The latter are limited by the difficulty encountered when trying to integrate the device with a force-sensing cantilever. The highest spatial resolution reported for a Hall bar operating at room temperature is 50 nm. Due to quantum effects (long mean free path), scaling down devices based on high mobility material results in a drop in sensitivity. For magnetic material studies of current interest higher resolutions are required. To achieve this goal in a material system which is compatible with micromachining the proposed approach utilises silicon as the sensing material. Silicon Hall bars have already been reported to work for large scale devices. This thesis presents the development of p-type enhancement mode MOSFET transistor fabrication process on a tip of Atomic Force Microscope (AFM) probe. The active device fabrication process was developed in order to allow fabrication of a magnetic sensor for Scanning Hall Probe Microscope (SHPM). The Hall bar was constructed on the apex of the AFM tip of attractive mode probes. The fabrication is performed in batches by using common semiconductor techniques leading to micromachining of the Si substrate, formation of the active device and cantilever release step. The transistor characteristics are presented, compared with expected performance of the modelled device and the reasons for differences are discussed. In this work, a method for application of spin-on-dopant on highly topographic structures is developed. Other encountered process incompatibilities are dealt with to finally present a full process for p-type enhancement mode MOSFET transistor on AFM tip fabrication.
13
Turner, Ian James. "AFM investigations of critical interactions in the Bacillus primosome and Cryogenic AFM : a new tool for structural biology". Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10188/.
Testo completoAbstract (sommario):
In this thesis for the first AFM has been employed for the high resolution imaging of a protein assembly. The DnaB-DnaG Helicase-Primase interaction in Bacillus is the key reaction that causes the switch from primase mode to polymerisation mode. This assembly was imaged using the AFM to a sub-molecular resolution revealing structural detail of the interaction. It is shown that the binding of the primase causes the structure of the helicase to switch from a hexamer to a trimer of dimers with one primase molecule bound to each dimer; also the existance of sub-populations with one and two primases bound suggests a sequential mode of binding. Recently crystallography data has been published that confirms the structural observations generated by AFM here. This is the first time that AFM and crystallography data have been used concurrently to solve the molecular structure of a protein assembly and it shows the potential application of AFM for sub-molecular resolution imaging of other protein assemblies. The role of DnaD in the Bacillus primosome is well established, however, its exact function was unknown. In this thesis AFM was applied to help solve this biomolecular problem, it revealed that DnaD has a pivotal role in early primosome assembly, opening up the DNA allowing other components of the cascade to bind. DnaD was shown to cause supercoiled DNA to adopt an open circular formation; this reaction was shown to be both reversible and universally applicable to all sequences of DNA. Comparisons are made between the role of DnaD and the roles of the histone-like proteins H-NS and HU. These experiments show that AFM can be applied to the imaging of proteins and their interactions with DNA and used to solve biomolecular problems that other techniques cannot solve. The design and implementation of a novel cryogenic AFM system for the imaging of biomolecules at subzero temperatures was executed. Preliminary results show that such a system has the potential to reduce the two main intrinsic effects limiting current AFM imaging; sample softness and thermal motion. The application of AFM in this thesis shows its strength as a tool in molecular biology not only for the high resolution imaging of proteins and protein assemblies but also as a technique that can be uniquely applied to solve biomolecular problems. This thesis also shows for the first time that AFM can be applied to generate sub-molecular resolution of protein assemblies. The strength of the AFM data when combined with crystallography data shows that AFM is a very powerful tool for the imaging of protein assemblies; it could even become the technique of choice
14
Mege, Fabrice. "AFM à contact résonant : développement et modélisation". Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00618676.
Testo completoAbstract (sommario):
Avec l'intégration de circuits intégrés de plus en plus denses, le besoin d'outils de caractérisation adaptés à ces échelles se fait ressentir. Identifier et analyser les problèmes de fiabilité survenant dans ces structures à des dimensions inférieures à 100 nm demande la mise au point d'instruments innovants. Ce travail de thèse a consisté dans un premier temps à développer un appareil à champs proches sensible aux propriétés mécaniques de surface, et dans un second temps à analyser les résultats expérimentaux en s'appuyant sur des approches analytiques et/ou numériques. Désigné sous le nom de microscope à force atomique à résonance de contact (CR-AFM), cet appareil est sensible à la rigidité effective de films minces sur substrat, ce qui lui permet de cartographier la rigidité mécanique de films minces. Nous avons mené un important travail de développement instrumental afin d'obtenir des résultats expérimentaux répétables et fiables, condition indispensable à une analyse quantitative. Puis nous avons utilisé le CR-AFM sur divers échantillons : empilements modèles (films de silice sur silicium, avec épaisseurs variables de silice), films de silice avec porosité variable, structures damascènes d'interconnexion cuivre,... Des images traduisant les variations d'élasticité de surface ont ainsi pu être construites. Pour quantifier ces variations, nous avons analysé nos résultats à l'aide de différents modèles (approches analytiques et numériques). Des simulations par éléments finis ont été réalisées pour étayer ces résultats.
15
Hugel, Thorsten. "Towards Synthetic Molecular Motors Interfaced by AFM". Diss., lmu, 2003. http://nbn-resolving.de/urn:nbn:de:bvb:19-8157.
Testo completo
16
Kufer, Stefan. "AFM-basierte Assemblierung biomolekularer Bausteine auf Festkörperoberflächen". Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-96805.
Testo completo
17
Rivera, Ahlin Alexander. "Noise squeezing and parametricamplication in dynamic AFM". Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-225974.
Testo completo
18
Rieger, Johannes. "AFM manipulation of damping in nanomechanical resonators". Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-159621.
Testo completoAbstract (sommario):
Ein bedeutender Teilbereich der Nanomechanik beschäftigt sich mit der Erforschung kleiner, schwingender Systeme, welche aufgrund ihrer geringen Massen auf minimale Umgebungseinflüsse reagieren.
Dies macht derartige nanoskalige Resonatoren zu äußerst empfindlichen Sensoren.
Die fortschreitende Miniaturisierung nanomechanischer Systeme erfordert nun einerseits die Weiterentwicklung von Antriebs- und Detektionsmechanismen, andererseits spielt die Verbesserung der mechanischen Güte eine zentrale Rolle für die Erhöhung der Empfindlichkeit möglicher sensorischer Anwendungen.
Hierfür ist die Untersuchung der Mechanismen, welche die mechanische Dämpfung der Resonatoren verursachen, erforderlich.
Um das Dämpfungsverhalten eines beidseitig eingespannten nanomechanischen Siliziumnitridresonators zu untersuchen und zu kontrollieren wird in dieser Arbeit ein Rasterkraftmikroskop (AFM) eingesetzt.
Dessen Spitze wird mit dem Resonator in Kontakt gebracht und beeinflusst als lokale Störung kontrolliert das nanomechanische System.
Das AFM bildet hierbei einen mechanischen Punktkontakt mit der Aufhängung des Resonators aus, wodurch Schwingungsenergie vom Resonator in die AFM-Spitze abgeleitet wird.
Aufgrund der hervorragenden räumlichen Auflösung des Rasterkraftmikroskops ist es somit möglich den ortsaufgelösten Energiefluss zwischen den beiden Systemen zu untersuchen.
Hierfür wird die mechanische Resonanz der Siliziumnitridsaite im Radiofrequenzbereich mittels eines heterodynen Überlagerungsverfahrens elektrisch ausgelesen.
Die Bewegung des zwischen zwei Goldelektroden platzierten Resonators ruft eine Kapazitätsänderung des durch die Elektroden gebildeten Kondensators hervor.
Durch Kopplung an einen Mikrowellenschwingkreis kann diese Kapazitätsänderung ausgelesen werden.
Zudem können Gleich- und Wechselspannungen an die Elektroden angelegt werden, wodurch einerseits die Resonanzfrequenz des Resonators verstimmt und andererseits die mechanische Bewegung angetrieben werden kann.
Das derart angetriebene nanomechanische System kann nun unter Einfluss der lokalen Störung durch das AFM in positions- und kraftabhängigen Messungen untersucht werden.
Es zeigt sich, dass der Energietransfer durch den mechanischen Punktkontakt einen äußerst starken Einfluss auf die mechanische Güte des Siliziumnitridbalkens hat, seine Resonanzfrequenz jedoch nur geringfügig beeinflusst wird.
Dies kann durch eine Änderung der mechanischen Impedanzanpassung des Resonators an seine Umgebung erklärt werden.
Die Impedanzänderung durch den mechanischen Punktkontakt ermöglicht den Übergang eines stark fehlangepassten nanomechanischen Systems hoher Güte zu einem angepassten System niedriger Güte auf einem einzigen Resonator.
Hierbei bleibt die intrinsische Dämpfung des Resonators unverändert und die zusätzlich induzierte Dämpfung kann der Abstrahlung von Vibrationsenergie in die Umgebung zugeschrieben werden.
Resonatoren hoher Güte ergeben sich somit als Systeme mit möglichst großer Fehlanpassung der mechanischen Impedanz.
Desweiteren kann mit dieser Methode das in den Aufhängepunkt des Resonators hineinreichende Verzerrungsfeld abgebildet werden.
Dies ermöglicht die Untersuchung gekoppelter Moden des Resonators sowie deren Modenform.
19
Samsuri, Fahmi B. "Single Cell analysis using AtomicForce Microscopy (AFM)". Thesis, University of Canterbury. Electrical and Computer Engineering, 2010. http://hdl.handle.net/10092/5516.
Testo completoAbstract (sommario):
Replication of biological cells for the purpose of imaging and analysis under
electron and scanning probe microscopy has facilitated the opportunity to
study and examine some molecular processes and structures of living cells in
a manner that were not possible before. The difficulties faced in direct
cellular analysis when using and operating Atomic Force Microscopy (AFM)
in situ for morphological studies of biological cells have led to the
development of a novel method for biological cell studies based on
nanoimprint lithography. The realization of the full potential of high
resolution AFM imaging has revealed some very important biological events
such as exocytosis and endocytosis. In this work, a soft lithography
Bioimprint replication technique, which involved simple fabrication steps,
was used to form a hard replica of the cell employing a newly developed
biocompatible polymer that has fast curing time at room temperature
essential for this process. The structure and topography of the rat muscle cell
and the endometrial (Ishikawa) cancer cell were investigated in this study.
Cells were cultured and incubated in accordance with standard biological
culturing procedures and protocols approved by the Human Ethics
Committee, University of Otago. An impression of the cell profile was
created by applying a layer of the polymer onto the cells attached to a
substrate and rapidly cured under UV-light. Fast UV radiation helps to lock
cellular processes within seconds after exposure and replicas of the cancer
cells exhibit ultra-cellular structures and features down to nanometer scale.
Elimination of the AFM tip damping effects due to probing of the soft
biological tissue allows imaging with unprecedented resolution. Highxx
resolution AFM imagery provides the opportunity to examine the structure
and topography of the cells closely so that any abnormalities can be
identified. Craters that resemble granules and features down to 100 nm were
observed. These represent steps on a transitional series of sequential
structures that indicate either an endocytotic or exocytotic processes, which
were evident on the replicas. These events, together with exocytosis, play a
very significant part in the tumorigenesis of these cancer cells. By forming
cell replica impressions, not only have they the potential to understand
biological cell conditions, but may also benefit in synthesizing three
dimensional (3-D) scaffolds for natural growth of biological cells and
providing an improvement over standard cell growth conditions. Further
examinations by observing the characteristic behaviour of the plasma
membrane when the cells were induced by certain compound such as cobalt
chloride (CoCl2) under control and stimulated conditions have brought in the
opportunity to examine the effect of this stimulant in inducing apoptosis in
many different kinds of cells. Numbers of pores formed on the cells
membrane were found to increase significantly after the cells where induced
with CoCl2 that correlated well with the level of vascular endothelial growth
factor (VEGF) receptors expression, which contributed to tumour growth.
This indicates CoCl2 has exaggerated the expression of the VEGF growth
factor. Investigations were also done to the cells using functionalized nanoparticles
as bio-markers to establish the connection between exocytosis with
nanopores found on the membrane surfaces of the cells. These microbeads
were found attached to sites surrounding the nucleus of the cell and higher
numbers of visible beads would confirm that there was an up-regulation of
the VEGF expression in cells induced by CoCl2. All these can contribute to
expanding the knowledge about exocytosis and fundamental physiology of
cells, and also assist in understanding diseases especially cancer.
20
Pearson, Anita P. "AFM investigation of single molecule force measurements". Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441016.
Testo completo
21
Elkaseh, Akram Abdulsalam. "Fabrication of Josephson junctions using AFM nanolithography". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5421.
Testo completoAbstract (sommario):
Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.Dissertation presented for the degree of Doctor of Philosophy in Engineering at the University of Stellenbosch
ENGLISH ABSTRACT: Planar weak link structures, such as micro-bridges, variable thickness bridges and nanobridges, have always attracted a lot of attention. Their potential to behave as real Josephson elements make them useful devices, with numerous applications. Powerful techniques, such as focused ion-beam and electron-beam lithography, were successfully used and are well understood in planar weak link structure fabrication. In this dissertation the results of an experimental study on planar weak link structures are presented. For the first time these structures have been successfully fabricated using AFM nanolithography on hard high-temperature superconducting YBCO tracks, where diamond coated silicon tips were used as a ploughing tool. Superconducting YBCO thin films were deposited on different substrates, using inverted cylindrical magnetron sputtering. The films were used to fabricate micro-bridges, variable thickness bridges and nano-bridges, by using conventional photolithography, argon ion-beam milling and AFM nanolithography. The measured I-V characteristics of the fabricated micro-bridges (width down to 1.9 µm), variable thickness bridges (thickness down to 15 nm) and nano-bridge (width down to 490 nm) showed well defined DC and AC Josephson effect characteristics. For better understanding of the behaviour of these types of weak links, critical current versus temperature measurements, and magnetic field modulation of the critical current measurements, were also performed, with the results and discussions given inside the chapters. The major challenges that were experienced in the laboratory during the fabrication processes and the operation of the fabricated devices are also discussed, with the solutions given where appropriate.
AFRIKAANSE OPSOMMING: Swak-skakel vlakstrukture, soos mikrobr.ue, br.ue met veranderlike dikte en nanobr.ue, het nog altyd baie aandag getrek. Hul het die potensiaal om soos werklike Josephson-elemente te kan funksioneer en is, as gevolg hiervan, nuttige toestelle met veelvuldige toepassings. Kragtige tegnieke, soos gefokuste ioonstraal- en elektronstraal litografie, is suksesvol gebruik en word goed verstaan in die vervaardiging van swak-skakel vlakstrukture. In hierdie proefskrif word die resultate van ¡¦n eksperimentele studie van swak-skakel vlakstrukture voorgel.e. Vir die eerste keer is hierdie strukture suksesvol vervaardig, deur gebruik te maak AFMnanolitografie op harde, ho¡Le-temperatuur supergeleier YBCO (Yttrium Barium Koperoksied) spore, waar diamantbedekte silikonpunte gebruik is as ploeginstrument. ¡¦n Dun lagie van supergeleidende YBCO is op verskillende substrate gedeponeer, deur gebruik te maak van omgekeerde silindriese magnetron verstuiwing. Die dun lagies is gebruik in die vervaardiging van mikrobr.ue, br.ue met veranderlike dikte en nanobr.ue, deur die gebruik van gewone fotolitografie, argon-ioonstraal frees en AFM nanolitografie. Die gemete I-V eienskappe van die vervaardigde mikrobr.ue (met breedte so laag as 1.9 µm), veranderlike-dikte br.ue (dikte tot 15 nm) en nanobr.ue (breedte so min as 490 nm) toon goed gedefinieerde GS en WS eienskappe van die Josephson-effek. Ten einde die gedrag van hierdie tipes swak-skakels beter te kan verstaan, is metings gedoen van kritieke stroom teenoor temperatuur, asook magnetiese veld modulasie van die kritieke stroom. Hierdie resultate en besprekings daarvan word binne die toepaslike hoofstukke aangebied. Die grootste uitdagings wat in die laboratorium, sowel as met die toetsing van die vervaardigde toestelle ondervind is, word ook bespreek. Waar moontlik, word toepaslike oplossings voorgestel.
22
Pavelec, Jiří. "Vývoj lineárního posuvu pro UHV STM/AFM". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229812.
Testo completoAbstract (sommario):
The aim of this diploma thesis is to develop a linear positioning stage for Ultra High Vacuum (UHV) environment. Simple prototypes of the linear positioning stage were designed and incorporated as part of a multiaxis sample manipulator for a UHV Scanning Tunneling Microscopy / Atomic Force Microscopy (STM/AFM). Different types of position encoders and linear guideways are discussed. Implementation of the homodyne interferometer as an optimization tool for a slip-stick based linear stage is described. Scalar diffraction theory is used to model the diffraction grating optical position encoder behavior.
23
Jang, Chang-Hyun. "AFM-Assisted Nanofabrication using Self-Assembled Monolayers". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11103.
Testo completoAbstract (sommario):
This study describes the covalent and the electrostatic attachment of molecules, nano-particles, and proteins to patterned self-assembled monolayers. A scanning probe nanografting technique was employed to produce patterns of various sizes, down to 10 nm. Thus, we are able to demonstrate a degree of surface patterning which is an order of magnitude smaller than that used in the semiconductor industry.
One efficient strategy for creating chemically specific nanostructures is to use the extraordinary catalytic properties of enzymes. However, as the dimension of a catalyst patch is reduced down to nanometer scale, it is difficult to detect the very low concentration of product. This study resolves the problem by developing a new strategy: the surface trapping of a product generated by a nanometer-scale patch of surface-bound enzyme.
An array of proteins finds use when the array contains a number of different proteins. Toward this end, a new and convenient method for immobilizing enzymes is developed, which will allow the preparation of thin films containing several different catalytically-active enzymes on the nanoscale.
The disadvantage of scanning probe nanografting technique is that the AFM tip loses resolution through wear during the patterning procedure. This study examines the possibility of developing a new AFM lithographic method to avoid wear: the use of enzymes covalently attached to a tip as a site-specific catalyst.Ph. D.
24
Neugirg, Benedikt R., Sean R. Koebley, Hannes C. Schniepp e Andreas Fery. "AFM-based mechanical characterization of single nanofibres". Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A36361.
Testo completoAbstract (sommario):
Nanofibres are found in a broad variety of hierarchical biological systems as fundamental structural units, and nanofibrillar components are playing an increasing role in the development of advanced functional materials. Accurate determination of the mechanical properties of single nanofibres is thus of great interest, yet measurement of these properties is challenging due to the intricate specimen handling and the exceptional force and deformation resolution that is required. The atomic force microscope (AFM) has emerged as an effective, reliable tool in the investigation of nanofibrillar mechanics, with the three most popular approaches—AFM-based tensile testing, three-point deformation testing, and nanoindentation—proving preferable to conventional tensile testing in many (but not all) cases. Here, we review the capabilities and limitations of each of these methods and give a comprehensive overview of the recent advances in this field.
25
Swinford, Richard William. "An AFM-SIMS Nano Tomography Acquisition System". PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3485.
Testo completoAbstract (sommario):
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.
26
Kábrtová, Denisa. "Studium vlastností synteticky připraveného thaumasitu". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372197.
Testo completoAbstract (sommario):
The thesis is focused on the optimization of the thaumasite preparation in the way of ternesite hydration and further comparison of this approach to the other methods. The thaumasite was prepared by three different methods for this purpose - according to Aguilera et al., Purnell and the hydration method of ternesite clinkers. Finally, the X-ray diffraction analysis was particularly used to evaluate the obtained properties and results.
27
Kolaja, Filip. "Sledování termodynamické stability ettringitu v závislosti na zvolených vnitřních a vnějších parametrech". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392342.
Testo completoAbstract (sommario):
This diploma thesis is focused on long term monitoring of thermodynamic stability of ettringite under selected conditions and its possible destabilization or transformation into another AFt phase, especially thaumasite. Ettringite samples were made in two ways, by hydrating the yeelimite in the system with the alite and by addition of aluminium sulphate and calcium hydroxide.
28
Gamsjaeger, Roland. "AFM and SPR on biological systems applying atomic force microscopy (AFM) and surface plasmon resonance (SPR) to biologically important systems". Saarbrücken VDM Verlag Dr. Müller, 2007. http://d-nb.info/988909820/04.
Testo completo
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Le, Sueur Hélène. "Un AFM-STM cryogénique pour la physique mésoscopique". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00261434.
Testo completoAbstract (sommario):
La spectroscopie électronique basée sur l'effet tunnel donne accès à la densité d'états des électrons (DoS) dans les matériaux conducteurs, et renseigne ainsi en détail sur leurs propriétés électroniques. Au cours de cette thèse, nous avons développé un microscope permettant d'effectuer la spectroscopie tunnel résolue spatialement (10 nm) de nanocircuits individuels, avec une résolution en énergie inégalée (10 µeV). Cet appareil combine les fonctions de Microscopie par Force Atomique (mode AFM) et de spectroscopie Tunnel locale (mode STM), et fonctionne à 30 mK. Dans le mode AFM, la topographie de l'échantillon est imagée grâce à un diapason en quartz piézoélectrique, ce qui permet de repérer les circuits. La spectroscopie tunnel peut ensuite être faite sur les zones conductrices.
Avec ce microscope, nous avons mesuré la DoS locale dans une structure hybride Supraconducteur-métal Normal-Supraconducteur (S-N-S). Dans un tel circuit, les propriétés électroniques de N et de S sont modifiées par l'effet de proximité supraconducteur. Notamment, pour des fils N courts, nous avons pu observer -comme prédit- la présence d'un gap dans sa DoS, indépendant de la position dans la structure : le “minigap”. De plus, en modulant la phase supraconductrice entre les deux S, nous avons mesuré la modification de ce gap, et sa disparition lorsque la différence de phase vaut π.
Nos résultats expérimentaux pour la DoS, ainsi que ses dépendances en phase, en position, et en longueur de N sont en accord quantitatif avec les prédictions de la théorie quasiclassique de la supraconductivité. Certaines de ces prédictions sont observées pour la première fois.
30
Oral, Hasan Giray. "Modeling time-resolved interaction force mode AFM imaging". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43691.
Testo completoAbstract (sommario):
Intermittent contact mode atomic force microscopy has been widely employed for simultaneous topography imaging and material characterization. The work in the literature includes both qualitative and quantitative methods. Regular AFM cantilevers are generally used in these methods, yet these cantilevers come with certain limitations. These limitations result from the very nature of cantilever probes. They are passive force sensors with insufficient damping. This prevents having active and complete control on tip-sample forces, causing sample damage and inaccurate topography measurement. Ideally, an AFM probe should offer high bandwidth to resolve interaction forces, active control capability for small interaction force and stable operation, and sufficient damping to avoid transient ringing which causes undesired forces on the sample. Force sensing integrated readout and active tip (FIRAT) probe offers these properties. A special imaging mode, time-resolved interaction force (TRIF) mode imaging can be performed using FIRAT probe for simultaneous topography and material property imaging. The accuracy of topography measurement of samples with variations in elastic and adhesive properties is investigated via numerical simulations and experiments. Results indicate that employing FIRAT probe's active tip control (ATC) capability during TRIF mode imaging provides significant level of control over the tip-sample forces. This improves the accuracy of topography measurement during simultaneous material property imaging, compared to conventional methods. Moreover, Active tip control (ATC) preserves constant contact time during force control for stable contact while preventing loss of material property information such as elasticity and adhesive forces.
31
Gröger, Roland [Verfasser]. "Nanokontaktdrucken mit AFM-gesteuert phasenseparierten Blockcopolymerschichten / Roland Gröger". Karlsruhe : Forschungszentrum Karlsruhe, 2007. http://d-nb.info/986521612/34.
Testo completo
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Ramanujan, Chandra Sekar. "AFM and nanomechanics in ambient and liquid environments". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414222.
Testo completo
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Dunlop, Alex William. "Towards polymer sequencing using AFM-based force spectroscopy". Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493471.
Testo completoAbstract (sommario):
Force spectroscopy, performed on an atomic force microscope (AFM), has been used in the conventional sense to investigate specific tip-sample interactions, and also in a non-conventional manner to demonstrate the technique's potential as a polymer sequencing device.
34
Álvarez-Asencio, Rubén. "Nanotribology, Surface Interactions and Characterization : An AFM Study". Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145727.
Testo completoAbstract (sommario):
When two surfaces achieve contact, then contact phenomena such as adhesion, friction and wear can occur, which are of great interest in many disciplines, including physics, physical chemistry, material chemistry, and life and health sciences. These phenomena are largely determined by the nature and magnitude of the surface forces such as van der Waals, capillary and hydration forces. Moreover these forces are length-dependent, and therefore when the system scales down, their contribution scales up, dominating the interaction between the surfaces. A goal of my PhD work was to investigate fundamental contact phenomena in terms of the surface forces that regulate their properties. The primary tool applied in this PhD thesis work has been the atomic force microscopy (AFM), which (with all of its sub-techniques) offers the possibility to study such forces with high resolution virtually between all types of materials and intervening media. Therefore, in this work it was possible to study the long ranged interactions presented in air between different industrially relevant materials and how these interactions are shielded when the systems are immersed in an ionic liquid. Also investigated was the influence of microstructure on the tribological properties of metal alloys, where their good tribological properties were related with the vanadium and nitrogen contents for a FeCrVN tool alloy and with the chromium content for a biomedical CoCrMo alloy. Moreover, the effect of the intervening media can significantly affect the surface properties, and when the biomedical CoCrMo alloy was immersed in phosphate buffer saline solution (PBS), repulsive hydration forces decreased the friction coefficient and contact adhesion. On the other hand, with the immersion of the FeCrVN tool alloy in the NaCl solution, small particles displaying low adhesion were generated in specific regions on the surface with low chromium content. These particles are assumed to be related to a prepitting corrosion event in the tool alloy. The mechanical properties of stratum corneum (SC), which is the outermost layer of the skin, were also studied in this work. The SC presents a highly elastic, but stiff surface where the mechanical properties depend on the nanoscale. A novel probe has been designed with a single hair fibre in order to understand how the skin deforms locally in response to the interaction with such a fibre probe. This study revealed that is mostly the lateral scale of the deformation which determines the mechanical properties of the SC. Finally, important achievements in this work are the developments of two new techniques - tribological property mapping and the Hybrid method for torsional spring constant evaluation. Tribological property mapping is an AFM technique that provides friction coefficient and contact adhesion maps with information attributed to the surface microstructure. The Hybrid method is an approach that was originally required to obtain the torsional spring constants for rigid beam shaped cantilevers, which could not be previously determined from their power torsional thermal spectra (conventional method). However, the applicability is shown to be general and this simple method can be used to obtain torsional spring constants for any type of beam shape cantilever.QC 20140603
35
Elmouelhi, Ahmed (Ahmed M. ). 1979. "Genome scanning : an AFM-based DNA sequencing technique". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/34149.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (p. 157-160).
Genome Scanning is a powerful new technique for DNA sequencing. The method presented in this thesis uses an atomic force microscope with a functionalized cantilever tip to sequence single stranded DNA immobilized to a mica surface. The functionalized cantilever tip hybridizes with only one base type (A, C, T, or G) and results in distinct peaks in the AFM-produced image. Genome Scanning has been successful at identifying 40 base strands of synthesized DNA and has been shown to detect a particular base type on 48 kilobase strands of lambda DNA. Currently, Genome Scanning is only accurate to 3-26 bases at a time, however, it can achieve a sequencing speed of 6000 bases/sec. In other words, Genome Scanning can be used to sequence the 3 billion bases of the human genome in 5.78 days.
by Ahmed Elmouelhi.
S.M.
36
Wang, XiuZhu. "Investigation of biological and chemical interactions by AFM". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615986.
Testo completo
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Pinto, Diego Kops. "Nano-oxidação do silício utilizando sonda de AFM". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-09012008-154136/.
Testo completoAbstract (sommario):
A oxidação anódica local utilizando o Microscópio de Força Atômica (AFM - Atomic Force Microscopy) foi investigada aplicando-se uma tensão negativa entre sonda de nitreto de silício e superfícies de Si. Todas as amostras foram limpas em uma solução de 1 NH4OH (30%): 1H2O2 (38%): 4H2O(DI) a 80ºC conhecida na literatura como SC1 (Standard Cleaning 1) ou, alternativamente, uma imersão em solução diluída de ácido hidrofluorídrico seguido de SC1 ou fervura em álcool isopropílico. As nano-oxidações consistiram de padrões quadrados localizados de óxido com área de 0,25 µm² e foram obtidos através do crescimento de linhas paralelas com espaço e comprimento interlinear constante (<2 nm) e várias varreduras dos quadrados em uma mesma área. Das análises de AFM, foram obtidos perfis transversais e 3D, os quais foram empregados na obtenção da espessura do óxido como função da tensão aplicada, número de varreduras e intervalo de tempo após a limpeza SC1. Foi observado que a espessura aumenta com a tensão negativa aplicada e com o número de varreduras. Também foram realizadas simulações para levantar as distribuições de tensão e de campo elétrico no sistema sonda-ar-silício ou sonda-ar-óxido-silício(substrato). Observou-se uma oxidação local assistida por um alto campo elétrico capaz de induzir difusão iônica local finita na extremidade da sonda. Foi simulado também o efeito das diferentes terminações de sonda do AFM, circular ou pontiaguda, no campo elétrico e na queda de tensão. Foram também realizadas oxidações com sondas recobertas com ouro em superfícies de Si precedidas de imersão simples em solução de ácido hidrofluorídrico seguido ou não do procedimento de limpeza SC1. Por fim, análises de absorção por infravermelho (FTIR) foram realizadas em superfícies de Si oxidadas por AFM para analisar a estrutura dos óxidos anódicos obtidos. A oxidação anódica utilizando sondas de nitreto de silício ocorre apenas após pré-limpeza terminada com SC1, sendo catalisada pelos altos campos elétricos (_ 106 V/cm), tendo como elementos reagentes, as espécies H2O adsorvidas e o óxido nativo hidrolisado na superfície após a etapa de limpeza SC1.Local anodic oxidation of silicon using Atomic Force Microscopy (AFM) was investigated by applying a negative voltage between silicon nitride tip and Si surfaces. All samples were cleaned with an ammonium-based solution known in literature as standard cleaning 1 (SC1) or a dip in a diluted hydrofluoric acid solution followed by SC1 or, also, boiling in isopropyl alcohol. Localized squares patterns of oxide, 0.25 µm² in area, were formed by growing parallel lines with constant interlinear spacing and length and several scans in the same area. From AFM analysis with non-biased tip, it was obtained 3D and section profiles, which were used to obtain the oxide thickness as a function of the applied voltage, number of scans and interval of time after SC1 cleaning. It was noteworthy that thickness increases with the applied negative voltage and with the number of scans. Simulations were performed in order to model voltage and electric field distributions of the system tip-air-silicon or tip-air-oxide-silicon(substrate) indicating a local oxidation assisted by high electrical field and local ionic diffusion of species. It was simulated the effect of tip termination, circular or sharpen, on the electric field and voltage distributions. In addition, oxidations were performed using Au coated tips onto Si surfaces previously dipped in diluted hydrofluoric acid solution followed or not by SC1 cleaning process. Finally, infrared absorption analysis (FTIR) were performed in order to analise the structure of the obtained anodic oxides. The anodic oxidation using silicon nitride tips has occurred only after SC1 precleaning step, being catalized by high electric field (_ 106 V/cm), having as reagents, the adsorbed water species and hydrolized native oxide on the surface after the SC1 cleaning step.
38
Eskandari, K., e H. Ghourchian. "AFM Investigation of Epoxy Fracture Surfaces Indicating Nanoplasticity". Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42511.
Testo completoAbstract (sommario):
Noble metal nanoparticles have a great potential for biological study, especially the use of gold nanoparticles is very popular. In this work gold nanoparticles (GNPs), silver nanoparticles (SNPs) and goldsilver hybrid nanoparticles (HNPs) synthesized and used as a carrier for electrochemical investigation of redox protein. Optical characterization of these nanoparticles was performed by UV-Vis spectroscopy. The maximum of the plasmon band for GNPs, SNPs and HNPs (ratio of 1:1) are 524, 392 and 455 nm respectively. The optical absorption spectra of HNPs solution shows only one plasmon absorption, it is concluded that mixing of gold and silver leads to a homogeneous formation of alloy nanoparticles. LCR meter study shows the HNPs is best conductance in compare of GNPs and SNPs. Therefore, the electron transfer of the homogenous GOx, HRP and Hb was investigates by electrochemical method in presence of HNPs. They demonstrated quasi-reversible cyclic voltammograms with a formal potential of -479, -178 and -168 mV in 50 mM phosphate buffer solution at pH 7.4 respectively.
39
Haba, D., M. Barbezat e A. J. Brunner. "AFM Investigation of Epoxy Fracture Surfaces Indicating Nanoplasticity". Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42653.
Testo completoAbstract (sommario):
Epoxy fracture surfaces are investigated by nanomechanical atomic-force micrsocopy (AFM). Apparent nodules on these surfaces are likely AFM tip-convolution artifacts, which might also explain apparent modulus inhomogeneities. No modulus inhomogeneities are found on smooth ultramicrotome cuts. Invest igation
of a copolymer shows, however, that existing inhomogeneities can be measured indeed. AFM investigation results in plastic deformation of ultramicrotome cuts already at low forces of 50 nN, which results in a blunt topographic image and an apparently increased modulus. This suggests that thin, sharp surface features are present on ultramicrotome cuts which are plastically deformed upon AFM investigation. Super-sharp AFM imaging showed a presumably more representative image of the investigated fracture surfaces,
which showed numerous depressions and vertical steps a few nanometers high. This suggests that even brittle epoxy exhibits some plasticity at the nanometer scale upon fracture.
40
Wang, Jialin. "AFM surface force measurements between hydrophobized gold surfaces". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29031.
Testo completoAbstract (sommario):
In 1982, Israelachvili and Pashley reported the first measurements of a hitherto unknown attractive force between two mica surfaces hydrophobized in cetyltrimethylammonium bromide (CTAB) solutions. Follow-up experiments conducted by many investigators confirmed their results, while others suggested that the â hydrophobic forceâ is an artifact due to nanobubbles (or cavitation). Evidences for the latter included the discontinuities (or steps) in the force versus distance curves and the pancake-shaped nano-bubbles seen in atomic force microscopic (AFM) images. Recent measurements conducted in degassed water showed, however, smooth force versus distance curves, indicating that the hydrophobic force is not an artifact due to nanobubbles.1, 2
Still other investigators3, 4 suggested that the long-range attraction observed between hydrophobic surfaces is due to the correlation between the patches of adsorbed ionic surfactant and the patches of unoccupied surface. For this theory to work, it is necessary that the charged patches be laterally mobile to account for the strong attractive forces observed in experiment. In an effort to test this theory, AFM force measurements were conducted with gold substrates hydrophobized by self-assembly of alkanethiols and xanthates of different chain lengths. The results showed long-range attractions despite the fact that the hydrophobizing agents chemisorb on gold and, hence, the adsorption layer is immobile.
When the gold surfaces were hydrophobized in a 1 Ã 10-3 M thiol-in-ethanol solution for an extended period of time, the force curves exhibited steps. These results indicate that the long-range attractions are caused by the coalescence of bubbles, as was also reported by Ederth.5 The steps disappeared, however, when the species adsorbed on top of the chemisorbed monolayer were removed by solvent washing, or when the gold substrates were hydrophobized in a 1 Ã 10-5 M solution for a relatively short period of time.
AFM force measurements were also conducted between gold substrates coated with short-chain thiols and xanthates to obtain hydrophobic surfaces with water contact angles (ï ±) of less than 90o. Long-range attractions were still observed despite the fact that cavitation is thermodynamically not possible.
Having shown that hydrophobic force is not due to coalescence of pre-existing bubbles, cavitation, or correlation of charged patches, the next set of force measurements was conducted in ethanol-water mixtures. The attractive forces became weaker and shorter-ranged than in pure water and pure ethanol. According to the Derjaguinâ s approximation6, an attractive force arises from the decrease in the excess free energy (ï §f) of the thin film between two hydrophobic surfaces.7 Thus, the stronger hydrophobic forces observed in pure water and pure ethanol can be attributed to the stronger cohesive energy of the liquid due to stronger H-bonding. Further, the increase in hydrophobic force with decreasing separation between two hydrophobic surfaces indicates that the H-bonded structure becomes stronger in the vicinity of hydrophobic surfaces.
The force measurements conducted at different temperatures in the range of 10-40ºC showed that the hydrophobic attraction between macroscopic surfaces causes a decrease in film entropy (Sf), which confirms that the hydrophobic force is due to the structuring of water in the thin film between two hydrophobic surfaces. The results showed also that the hydrophobic interaction entails a reduction in the excess film enthalpy (Hf), which may be associated with the formation of partial (or full) clathrates formed in the vicinity of hydrophobic surfaces. The presence of the clathrates is supported by the recent finding that the density of water in the vicinity of hydrophobic surfaces is lower than in the bulk.8Ph. D.
41
LI, LI. "NANOSCALE CHARGE DENSITY MEASUREMENT IN LIQUID WITH AFM". Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1599744539112356.
Testo completo
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Schwab, Lucien. "Sonde opto-mécaniques pour la microscopie AFM rapide". Thesis, Toulouse, INSA, 2020. http://www.theses.fr/2020ISAT0016.
Testo completoAbstract (sommario):
Dans le domaine de la microscopie, le microscope à force atomique (AFM), inventé en 1986, est aujourd’hui toujours basé sur le même concept de sonde de force : le levier. Les performances de l’AFM, et en particulier sa vitesse d'imagerie, sont principalement limitées par ce levier, dont la fréquence de résonance plafonne à quelques MHz. Ce travail de thèse présente un nouveau concept de sonde AFM, une sonde optomécanique (OM), ainsi que les développements sur l’instrument pour exploiter ses performances. En effet, des sondes OM vibrant à plus de 100 MHz sont développées et exploitées dans ce manuscrit. Elles démontrent une limite de détection thermomécanique remarquable de 4.5x1E-17 m/√Hz à température ambiante, inférieure à celle de toute autre sonde AFM, permettant un fonctionnement avec une amplitude de vibration de 10 pm. Cette sonde OM est constituée d'un anneau de silicium suspendu d'un diamètre de 20 µm, agissant à la fois comme un résonateur mécanique et un résonateur optique à mode de galerie. Les deux sont intimement couplés par la forme de l'anneau : lorsque l'anneau vibre dans un mode de respiration, la longueur de la cavité optique varie et sa longueur d'onde de résonance varie autour de la longueur d’onde centrale de 1,55 µm. De nombreuses variantes de sondes OM sont caractérisées pour trouver la conception optimale, conduisant à un gap de couplage évanescent de 100 nm à 200 nm et une largeur de rayons de suspension inférieure à 100 nm. Grâce à une caractérisation approfondie, un phénomène singulier est également mis en évidence : le super-mode. Deux alternatives pour mettre la sonde en vibration sont comparées : l’actionnement capacitif et optique. L'étude de la stabilité et du bruit de la sonde permet d'identifier une source de bruit supplémentaire en actionnement optique. Ensuite, les sondes OM sont intégrées dans un instrument AFM dont chaque composant est spécialement développé, du scanner piézoélectrique à l'acquisition et au traitement des données. À cause d’un verrou technologique de fabrication, la pointe de la sonde OM n’a pas pu être approchée d’une surface : elle ne dépasse pas du substrat sur lequel la sonde est fabriquée. Un levier AFM classique est donc utilisé pour interagir mécaniquement avec la sonde AFM. La bande passante de l'instrument est alors caractérisée en fonctionnement, démontrant une bande passante de boucle de rétroaction de 100 kHz, à l’état de l’art. Enfin, une première pseudo-image est réalisée avec ces sondes, démontrant le fonctionnement complet de l'instrumentIn the field of microscopy, the atomic force microscope (AFM) invented in 1986 was brought little, but nonetheless impressive, incremental developments since then. This instrument’s performances, and in particular imaging speed, are mainly limited by its cantilever-type force probe whose resonance frequency peaks at a few MHz. This thesis work presents a new concept of AFM probe, an optomechanical (OM) one, and custom instrument’s components to exploit its performances. Indeed, the 100+ MHz vibrating OM probes tested in this manuscript demonstrate an exquisite thermomechanical limit of detection of 4.5x1E-17 m/√Hz at room temperature, lower than any other AFM probe detection, and an instrument-limited 10 pm vibration amplitude. This OM probe consists of a suspended silicon ring with a 10 µm radius, acting as a mechanical resonator and a whispering-gallery-mode optical resonator. The two are intimately coupled by the ring shape: when the ring vibrates in a breathing mode, the optical cavity length varies and so does its resonance wavelength around its central value 1.55 µm. Characterization of numerous OM probes with different designs are investigated to find optimal designs, that is a 100 nm to 200 nm evanescent-coupling-gap and spokes width below 100 nm. Through deep characterization, acute phenomenon is also highlighted as the super-mode. Two alternatives to put the probe in vibration are compared: capacitive and optical. Stability and noise study of the probe help identify an additional noise source in optical actuation, that seem to be related to the optical background signal. Each developed component of the AFM instrument is detailed from piezoelectric scanner to data acquisition and processing. Because of a fabrication technological lock, the tip of the OM probe could not approach any surface as it did not protrude from the substrate on which the probe is made. A conventional AFM lever is therefore used to interact mechanically with the AFM probe. The instrument’s bandwidth is then characterized in operation, demonstrating a state-of-the-art 100 kHz feedback-loop bandwidth. Finally, a first pseudo-image is achieved with such probes, demonstrating the whole instrument operation
43
Starr, Michael J. "AFM-FTIR A New Technique for Materials Characterization /". Cincinnati, Ohio : University of Cincinnati, 2008. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1227192819.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Cincinnati, 2008.Advisor: James Boerio. Title from electronic thesis title page (viewed Feb.16, 2009). Includes abstract. Keywords: AFM; FTIR spectroscopy; atomic force microscopy; interphase; adhesive analysis; interferogram. Includes bibliographical references.
44
Dickinson, Laura Rickard. "Characterization of Interfacial Interactions By Functionalized Afm Probes". W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1477067892.
Testo completoAbstract (sommario):
Interfacial interactions play a crucial role in many complex materials systems, determining many of their properties. However, characterization of these interactions, especially at the micro- to nanometer length scales is experimentally challenging. Consequently, insufficient knowledge of these systems limits technological advances in important applications. In this work, custom functionalized atomic force microscopy (AFM) probes were developed to measure the interaction forces in two important systems: petroleum reservoirs and nanocomposites. Our work seeks a deeper understanding of the specific interactions that occur in these two systems so that modified approaches can be developed to improve them. Petroleum recovery is concerned with maximizing the collection of crude oil, which adheres to rock surfaces underground and resists release when flushed with injection water. to promote more efficient oil extraction, the injection water can be tailored to decrease this oil–rock adhesion. In our study of petroleum recovery, we coated a probe in crude oil and dried the oil to create a robust layer. By performing force measurements with this probe on a mica substrate and varying the surrounding aqueous composition, we observed the effect of multiple variables on the relevant forces in a reservoir, ultimately providing enhanced predictive capabilities for increased oil extraction in injection wells. to achieve a graphene oxide (GO) nanocomposite with optimal properties requires a strong bond between the nanofiller particles and surrounding polymer matrix. to this end, we studied the interactions within a GO–polymer nanocomposite by coating a probe in GO flakes and performing force measurements on polymer substrates. The preferential attraction between GO and some polymers is consistent with the results of recent interfacial tests performed in our lab. Our research provides crucial information for the selection of novel GO–polymer combinations, which can be implemented in superior reinforced nanocomposite systems. Through development of these novel tools, we anticipate that our customized probes will enhance predictive capabilities in the study of colloidal and other interfacial systems.
45
Pospíšilová, Klára. "Studium vlastností thaumasitu v dlouhodobém horizontu". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372084.
Testo completoAbstract (sommario):
This thesis deals with monitoring the thermodynamic stability of thaumasite and monitoring it is properties in the long term. The aim was to synthesize thaumasite under different conditions and to evaluate it using X-ray diffraction analysis and thermal analysis.
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DI, SANTO GIOVANNI. "Functionalization of c-Silicon surfaces for nanoscopic devices". Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/917310.
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Mutschler, Tina. "Charakterisierung bio- und chemosensitiver Schichten mit Ellipsometrie und AFM". [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972308059.
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Sarangapani, Krishna Kumar. "Characterizing selectin-ligand bonds using atomic force microscopy (AFM)". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/11650.
Testo completoAbstract (sommario):
The human body is an intricate network of many highly regulated biochemical processes and cell adhesion is one of them. Cell adhesion is mediated by specific interactions between molecules on apposing cell surfaces and is critical to many physiological and pathological processes like inflammation and cancer metastasis. During inflammation, blood-borne circulating leukocytes regularly stick to and roll on the vessel walls, which consist in part, adhesive contacts mediated by the selectin family of adhesion receptors (P-, E- and L-selectin). This is the beginning of a multi-step cascade that ultimately leads to leukocyte recruitment in areas of injury or infection.
In vivo, selectin-mediated interactions take place in a hydrodynamic milieu and hence, it becomes imperative to study these interactions under very similar conditions in vitro. The goal of this project was to characterize the kinetic and mechanical properties of selectin interactions with different physiologically relevant ligands and selectin-specific monoclonal antibodies (mAbs) under a mechanically stressful milieu, using atomic force microscopy (AFM).
Elasticity studies revealed that bulk of the complex compliance came from the selectins, with the ligands or mAbs acting as relatively stiffer components in the stretch experiments. Furthermore, molecular elasticity was inversely related to selectin length with the Consensus Repeats (CRs) behaving as Hookean springs in series. Besides, monomeric vs. dimeric interactions could be clearly distinguished from the elasticity measurements. L-selectin dissociation studies with P-selectin Glycoprotein Ligand 1 (PSGL-1) and Endoglycan revealed that catch bonds operated at low forces while slip bonds were observed at higher forces. These results were consistent with previous P-selectin studies and suggested that catch bonds could contribute to the shear threshold for L-selectin-mediated rolling By contrast, only slip bonds were observed for L-selectin-antibody interactions, suggesting that catch bonds could be a common characteristic of selectin-ligand interactions. Force History studies revealed that off-rates of L-selectin-sPSGL-1 (or 2-GSP-6) interactions were not just dependent on applied force, as has been widely accepted but in fact, depended on the entire history of force application, thus providing a new paradigm for how force could regulate bio-molecular interactions.
Characterizing selectin-ligand interactions at the molecular level, devoid of cellular contributions, is essential in understanding the role played by molecular properties in leukocyte adhesion kinetics. In this aspect, data obtained from this project will not only add to the existing body of knowledge but also provide new insights into mechanisms by which selectins initiate leukocyte adhesion in shear.
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Iden, Simon Riis. "Exploring possibilities in AFM studies of InAs/GaAs QDs". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16356.
Testo completoAbstract (sommario):
The main focus of this master thesis work has been to image InAs emph{quantum dots} (QDs) using emph{atomic force microscopy} (AFM), to identify and evaluate various image processing methods used to estimate the volume of the InAs QDs. The InAs QDs studied in this thesis work, had been deposited on GaAs substrates, using solid-source emph{molecular beam epitaxy} (MBE) before the thesis work started. The total QD volume was determined for all samples, using eight different estimation methods. The purpose of estimating the total QD volume, was to compare the total volume to the deposited volume.Previous studies on similar samples, have indicated that the total volume can be larger than the deposited volume during MBE growth. This discrepancy is explained by incorporation of Ga from the substrate during growth. This was not observed in this thesis work. One possible explanation is that the samples have oxidized; resulting in a lower measured height.In addition, the relationship between atomic steps, defects and the appearance of large QDs were studied. parTwo series of samples were studied: one in which the QD growth temperature was varied and one in which the amount of deposited InAs was varied. The total QD volumes were found to increase with the QD growth temperature and the deposited InAs thickness. Square-shaped defects and contours of 2D islands were observed in nearly all samples. Higher/multiple terraces seem to be related to regions of higher QD density.
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Mihai, Nicoleta D. "UV/Ozone Cleaning Studies of AFM Force Sensor Tips". Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/MihaiND2006.pdf.
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