Dissertations / Theses on the topic 'Near-field microscopy'
To see the other types of publications on this topic, follow the link: Near-field microscopy.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Near-field microscopy.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Szelc, Jedrzej. "THz imaging and microscopy : a multiplexed near-field TeraHertz microscope." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/209643/.
Full text
2
von, Ribbeck Hans-Georg. "THz Near-Field Microscopy and Spectroscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-163917.
Full textAbstract:
Imaging with THz radiation at nanoscale resolution is highly desirable for specific material investigations that cannot be obtained in other parts of the electromagnetic spectrum. Nevertheless, classical free-space focusing of THz waves is limited to a >100 μm spatial resolution, due to the diffraction limit. However, the scattering- type scanning near-field optical microscopy (s-SNOM) promises to break this diffraction barrier. In this work, the realization of s-SNOM and spectroscopy for the THz spectral region from 30–300 μm (1–10 THz) is presented. This has been accomplished by using two inherently different radiation sources at distinct experimental setups: A femtosecond laser driven photoconductive antenna, emitting pulsed broadband THz radiation from 0.2–2 THz and a free-electron laser (FEL) as narrow-band high-intensity source, tunable from 1.3–10 THz. With the photoconductive antenna system, it was demonstrated for the first time that near-field spectroscopy using broadband THz-pulses, is achievable. Hereby, Terahertz time-domain spectroscopy with a mechanical delay stage (THz-TDS) was realized to obtain spectroscopic s-SNOM information, with an additional asynchronous optical sampling (ASOPS) option for rapid far-field measurements. The near-field spectral capabilities of the microscope are demonstrated with measurements on gold and on variably doped silicon samples. Here it was shown that the spectral response follows the theoretical prediction according to the Drude and the dipole model. While the broadband THz-TDS based s-SNOM in principle allows for the parallel recording of the full spectral response, the weak average power of the THz source ultimately limits the technique to optically investigate selected sample locations only. Therefore, for true THz near-field imaging, a FEL as a high-intensity narrow- band but highly-tunable THz source in combination with the s-SNOM technique, has been explored. Here, the characteristic near-field signatures at wavelengths from 35–230 μm are shown. Moreover, the realization of material sensitive THz near-field imaging is demonstrated by optically resolving, a structured gold rod with a reso- lution of up to 60 nm at 98 μm wavelength. Not only can the gold be distinguished from the silica substrate but moreover parts of the structure have been identified to be residual resin from the fabrication process. Furthermore, in order to explore the resolution capabilities of the technique, the near-fields of patterned gold nano- structures (Fischer pattern) were imaged with a 50 nm resolution at wavelengths up to 230 μm (1.2 THz). Finally, the imaging of a topography-independent optical material contrast of embedded organic structures, at exemplary 150 μm wavelength is shown, thereby demonstrating that the recorded near-field signal alone allows us to identify materials on the nanometer scale. The ability to measure spectroscopic images by THz-s-SNOM, will be of benefit to fundamental research into nanoscale composites, nano-structured conductivity phenomena and metamaterials, and furthermore will enable applications in the chemical and electronics industriesDie Bildgebung mit THz Strahlung im Nanobereich ist höchst wünschenswert für genaue Materialuntersuchungen, welche nicht in anderen Spektralbereichen durchgeführt werden kann. Aufgrund des Beugungslimits ist kann jedoch mit klassischen Methoden keine bessere Auflösung als etwa 100 μm für THz-Strahlung erreicht werden. Die Methode der Streulicht-Nahfeldmikroskopie (s-SNOM) verspricht jedoch dieses Beugungslimit zu durchbrechen. In der vorliegenden Arbeit wird die Realisierung der Nahfeld-Mikroskopie und Spektroskopie im THz-Spektralbereich von 30–1500 μm (0.2–10 THz) präsentiert. Dies wurde mittels zweier grundsätzlich unterschiedlichen Strahlungsquellen an separaten Experimentaufbauten erreicht: Einer photoleitenden Antenne welche gepulste breitbandige THz-Strahlung von 0.2–2 THz emittiert, sowie einem Freie- Elektronen Laser (FEL) als schmalbandige hochleistungs Quelle, durchstimmbar von 1.3–10 THz. Mit dem photoleitenden Antennensystem konnte zum ersten mal demonstriert werden, dass mit breitbandigen THz-Pulsen Nahfeldspektroskopie möglich ist. Dazu wurde die übliche THz-Time-Domain-Spektroskopie (THz-TDS) zur Erhaltung der spektroskopischen s-SNOM Informationen, sowie asynchrones optisches Abtasten (ASOPS) für schnelle Fernfeld Spektroskopie eingesetzt. Die nahfeldspektroskopischen Fähigkeiten des Mikroskops wurden anhand von Messungen an Gold sowie unterschiedlich dotierten Siliziumproben demonstriert. Dabei konnte gezeigt werden, dass die spektrale Antwort den theoretischen Voraussagen des Drude- sowie Dipol Modells folgt. Während das breitband THz-TDS basierte s-SNOM spektroskopische Nahfelduntersuchungen zulässt, limitiert jedoch die schwache Ausgangsleistung der THz-quelle diese Technik insofern, dass praktisch nur Punktspektroskopie an ausgesuchten Probenstellen möglich ist. Für echte nanoskopische Nahfeldbildgebung wurde daher ein FEL als durchstimmbare hochleistungs THz-Quelle in Kombination mit der s-SNOM-Technik erforscht. Hierzu wurden die charakteristischen Nahfeld-Signaturen bei Wellenlängen von 35–230 μm untersucht, gefolgt von die Verwirklichung materialsensitiver THz Nahfeldbildgebung gezeigt an Goldstreifen mit bis zu 60 nm Auflösung. Dabei kann nicht nur das Gold von dem Glassubstrat unterschieden werden, sondern auch Ablagerungen als Überreste des Fabrikationsprozesses identifiziert werden. Um die Grenzen der Auflösungsmöglichkeiten dieser Technik zu sondieren, wurden weiterhin die Nahfelder von gemusterten Gold-Nanostrukturen (Fischer-Pattern) bei Wellenlängen bis zu 230 μm (1.2 THz) abgebildet. Hierbei wurde eine Auflösung von 50 nm festgestellt. Schliesslich konnte der topographieunabhängige Materialkontrast von eingebetteten organischen Strukturen, exemplarisch bei 150 μm Wellenlänge, gezeigt werden. Die Fähigkeit, spektroskopische Aufnahmen mittels der THZ-s-SNOM Technik zu erzeugen, wird der Grundlagenforschung und in der Nanotechnologie zu Gute kommen, und weiterhin Anwendungen in der Chemischen- und Halbleiterindustrie ermöglichen
3
Leong, Siang Huei. "Apertureless scanning near-field optical microscopy." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615953.
Full text
4
Neacsu, Corneliu Catalin. "Tip-enhanced near-field optical microscopy." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16284.
Full textAbstract:
Die vorliegende Arbeit beschreibt neue Entwicklungen im Verständnis und in der Umsetzung der optischen Nahfeldmikroskopie (scattering - type scanning near-field optical microscopy, s-SNOM) für die lineare und nichtlineare optische Bildgebung mit ultrahoher Auslösung und Empfindlichkeit. Die fundamentalen Mechanismen, die der Feldverstärkung am Ende von ultrascharfen metallischen Spitzen zugrunde liegen, werden systematisch behandelt. Die plasmonischen Eigenschaften der Spitze wurden erstmalig beobachtet, und ihre Bedeutung für die optische Kopplung zwischen Spitze und Probe sowie für die sich ergebende Einengung des Nahfeldes wird diskutiert. Ein aperturloses Nahfeldmikroskop für die spitzenverstärkte Ramanspektroskopie (tip-enhanced Raman spectroscopy, TERS) wurde entwickelt. Die Grundlagen der TERS und die wesentliche Rolle des plasmonischen Verhaltens der Spitze sowie die klare Unterscheidung von Nahfeld-Ramansignatur und Fernfeld-Abbildungsartefakten werden beschrieben. Nahfeld Raman Verstärkungsfaktoren von bis zu 10 wurden erreicht, was einer Feldverstärkung von bis zu 130 entspricht und Raman-Messungen bis auf Einzel-Molekül-Niveau ermöglichte. Die optische Frequenzverdopplung (second harmonic generation, SHG) an einzelnen Spitzen wurde untersucht. Aufgrund ihrer teilweise asymmetrischen Nanostruktur erlauben die Spitzen eine klare Unterscheidung von lokalen Oberflächen und nichtlokalen Volumenbeiträgen zur nichtlinearen Polarisation sowie die Analyse ihrer Polarisations- und Emissions-Auswahlregeln. Die spitzenverstärkte Frequenzverdopplungs-Spektroskopie und die räumlich hoch aufgelöste Abbildung auf Basis des dielektrischen Kontrasts werden demonstriert. Mit Hilfe einer phasen-sensitiven, Selbst-homodyn-Frequenzverdopplungs-s-SNOM-Abbildungsmethode kann die Oberflächen-Struktur der intrinsischen 180-Domänen im hexagonal multiferroischen YMnO aufgelöst werden.This thesis describes the implementation of scattering-type near-field optical microscopy (s-SNOM) for linear and nonlinear optical imaging. The technique allows for optical spectroscopy with ultrahigh spatial resolution. New results on the microscopic understanding of the imaging mechanism and the employment of s-SNOM for structure determination at solid surfaces are presented. The method relies on the use of metallic probe tips with apex radii of only few nanometers. The local-field enhancement and its dependence on material properties are investigated. The plasmonic character of Au tips is identified and its importance for the optical tip-sample coupling and subsequent near-field confinement are discussed. The experimental results offer valuable criteria in terms of tip-material and structural parameters for the choice of suitable tips required in s-SNOM. An near-field optical microscope is developed for tip-enhanced Raman spectroscopy (TERS) studies. The principles of TERS and the role of the tip plasmonic behavior together with clear distinction of near-field Raman signature from far-field imaging artifacts are described. TERS results of monolayer and submonolayer molecular coverage on smooth Au surfaces are presented. Second harmonic generation (SHG) from individual tips is investigated. As a partially asymmetric nanostructure, the tip allows for the clear distinction of local surface and nonlocal bulk contributions to the nonlinear polarization and the analysis of their polarization and emission selection rules. Tip-enhanced SH microscopy and dielectric contrast imaging with high spatial resolution are demonstrated. SHG couples directly to the ferroelectric ordering in materials and in combination with scanning probe microscopy can give access to the morphology of mesoscopic ferroelectric domains. Using a phase sensitive self-homodyne SHG s-SNOM imaging method, the surface topology of 180 intrinsic domains in hexagonal multiferroic YMnO is resolved.
5
LeBlanc, Philip R. "Dual-wavelength scanning near-field optical microscopy." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82911.
Full textAbstract:
A dual-wavelength Scanning Near-Field Optical Microscope was developed in order to investigate near-field contrast mechanisms as well as biological samples in air. Using a helium-cadmium laser, light of wavelengths 442 and 325 nanometers is coupled into a single mode optical fiber. The end of the probe is tapered to a sub-wavelength aperture, typically 50 nanometers, and positioned in the near-field of the sample. Light from the aperture is transmitted through the sample and detected in a confocal arrangement by two photomultiplier tubes. The microscope has a lateral topographic resolution of 10 nanometers, a vertical resolution of 0.1 nanometer and an optical resolution of 30 nanometers. Two alternate methods of producing the fiber probes, heating and pulling, or acid etching, are compared and the metal coating layer defining the aperture is discussed. So-called "shear-force" interactions between the tip and sample are used as the feedback mechanism during raster scanning of the sample. An optical and topographic sample standard was developed to calibrate the microscope and extract the ultimate resolution of the instrument. The novel use of two wavelengths enables the authentication of true near-field images, as predicted by various models, as well as the identification of scanning artifacts and the deconvolution of often highly complicated relationships between the topographical and optical images. Most importantly, the use of two wavelengths provides information on the chemical composition of the sample. Areas of a polystyrene film are detected by a significant change in the relative transmission of the two wavelengths with a resolution of 30 nanometers. As a biological application, a preliminary investigation of the composition of Black Spruce wood cell fibers was performed. Comparisons of the two optical channels reveal the expected lignin distributions in the cell wall.
6
Rea, Nigel P. "Interference and laser feedback optical microscopy." Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:989c9fca-947d-490c-9f34-38065a7c57d9.
Full textAbstract:
This thesis concerns the development of simple, compact scanning optical microscopes which can obtain confocal and interference images. The effects of feeding the reflected signal back into the laser cavity of a confocal microscope are investigated and exploited. Monomode optical fibres are used to perform the spatial filtering required for confocal microscopy and, later, as the source of reference beams for interferometry. The theory describing the basic operation of the microscopes is developed. The optical systems are modelled using scalar diffraction theory and the effects of optical feedback into the laser cavity are described, with the practical implications emphasised. A fully reciprocal arrangement of the microscope is developed, in which a single mode optical fibre both launches the signal towards the object and then collects the reflected signal. The fibre is shown to exhibit the spatial filtering properties required for the source and detector in a confocal microscope. It is shown that a semiconductor laser can be used as a detector of the amplitude of the object signal. This is first demonstrated by directing the microscope signal back into the laser cavity and measuring the variation of the optical intensity in the cavity itself. Comparable results are obtained when the variation of the junction voltage across the cavity is measured. It is also shown that the optical fibre is redundant in this system, since the lasing mode of the cavity itself is sufficiently small to adequately spatially filter the reflected signal. When a Helium-Neon laser is used as the source of illumination the effect of the feedback on the laser is seen to be very different, resulting in interferometry. It is shown that high frequency modulation techniques can be used to obtain both confocal images and surface profiles from the same system. This is first demonstrated using an optical feedback scheme in which the modulation of the optical path length of the object beam is controlled electrooptically. In an alternative scheme the images are obtained by calculation, rather than by using a control loop system. In this case the modulation is achieved mechanically. The theoretical limits for the resolutions of the systems described are discussed. It is shown that the lateral resolution of the surface profile systems is inherently non-linear with feature height. Finally, a semiconductor laser based microscope is developed which can obtain confocal images and surface profiles independently. The dependence of the wavelength on the injection current is exploited as a convenient means of introducing a phase shift into the feedback signal by which profilometry can be achieved. All the systems are described theoretically and demonstrated experimentally.
7
Thoma, Arne [Verfasser]. "Apertureless Scanning Terahertz Near Field Microscopy / Arne Thoma." München : Verlag Dr. Hut, 2011. http://d-nb.info/1011442043/34.
Full text
8
Lessard, Guillaume Quake Stephen R. "Apertureless near-field optical microscopy for fluorescence imaging /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05302003-145931.
Full text
9
Hadjipanayi, Maria. "Scanning near-field optical microscopy of semiconducting nano-structures." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442754.
Full text
10
Schneider, Susanne Christine. "Scattering Scanning Near-Field Optical Microscopy on Anisotropic Dielectrics." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1192105974322-82865.
Full textAbstract:
Near-field optical microscopy allows the nondestructive examination of surfaces with a spatial resolution far below the diffraction limit of Abbe. In fact, the resolution of this kind of microscope is not at all dependent on the wavelength, but is typically in the range of 10 to 100 nanometers. On this scale, many materials are anisotropic, even though they might appear isotropic on the macroscopic length scale. In the present work, the previously never studied interaction between a scattering-type near-field probe and an anisotropic sample is examined theoretically as well as experimentally. In the theoretical part of the work, the analytical dipole model, which is well known for isotropic samples, is extended to anisotropic samples. On isotropic samples one observes an optical contrast between different materials, whereas on anisotropic samples one expects an additional contrast between areas with different orientations of the same dielectric tensor. The calculations show that this anisotropy contrast is strong enough to be observed if the sample is excited close to a polariton resonance. The experimental setup allows the optical examination in the visible and in the infrared wavelength regimes. For the latter, a free-electron laser was used as a precisely tunable light source for resonant excitation. The basic atomic force microscope provides a unique combination of different scanning probe microscopy methods that are indispensable in order to avoid artifacts in the measurement of the near-field signal and the resulting anisotropy contrast. Basic studies of the anisotropy contrast were performed on the ferroelectric single crystals barium titanate and lithium niobate. On lithium niobate, we examined the spectral dependence of the near-field signal close to the phonon resonance of the sample as well as its dependence on the tip-sample distance, the polarization of the incident light, and the orientation of the sample. On barium titanate, analogous measurements were performed and, additionally, areas with different types of domains were imaged and the near-field optical contrast due to the anisotropy of the sample was directly measured. The experimental results of the work agree with the theoretical predictions. A near-field optical contrast due to the anisotropy of the sample can be measured and allows areas with different orientations of the dielectric tensor to be distinguished optically. The contrast results from variations of the dielectric tensor components both parallel and perpendicular to the sample surface. The presented method allows the optical examination of anisotropies of a sample with ultrahigh resolution, and promises applications in many fields of research, such as materials science, information technology, biology, and nanoopticsDie optische Nahfeldmikroskopie ermöglicht die zerstörungsfreie optische Unter- suchung von Oberflächen mit einer räumlichen Auflösung weit unterhalb des klas- sischen Beugungslimits von Abbe. Die Auflösung dieser Art von Mikroskopie ist unabhängig von der verwendeten Wellenlänge und liegt typischerweise im Bereich von 10-100 Nanometern. Auf dieser Längenskala zeigen viele Materialien optisch anisotropes Verhalten, auch wenn sie makroskopisch isotrop erscheinen. In der vorliegenden Arbeit wird die bisher noch nicht bestimmte Wechselwirkung einer streuenden Nahfeldsonde mit einer anisotropen Probe sowohl theoretisch als auch experimentell untersucht. Im theoretischen Teil wird das für isotrope Proben bekannte analytische Dipol- modell auf anisotrope Materialien erweitert. Während fÄur isotrope Proben ein reiner Materialkontrast beobachtet wird, ist auf anisotropen Proben zusätzlich ein Kontrast zwischen Bereichen mit unterschiedlicher Orientierung des Dielektrizitätstensors zu erwarten. Die Berechnungen zeigen, dass dieser Anisotropiekontrast messbar ist, wenn die Probe nahe einer Polaritonresonanz angeregt wird. Der verwendete experimentelle Aufbau ermöglicht die optische Untersuchung von Materialien im sichtbaren sowie im infraroten Wellenlängenbereich, wobei zur re- sonanten Anregung ein Freie-Elektronen-Laser verwendet wurde. Das dem Nahfeld- mikroskop zugrunde liegende Rasterkraftmikroskop bietet eine einzigartige Kombi- nation verschiedener Rastersondenmikroskopie-Methoden und ermöglicht neben der Untersuchung von komplementären Probeneigenschaften auch die Unterdrückung von mechanisch und elektrisch induzierten Fehlkontrasten im optischen Signal. An den ferroelektrischen Einkristallen Lithiumniobat und Bariumtitanat wurde der anisotrope Nahfeldkontrast im infraroten WellenlÄangenbereich untersucht. An eindomÄanigem Lithiumniobat wurden das spektrale Verhalten des Nahfeldsignals sowie dessen charakteristische Abhängigkeit von Polarisation, Abstand und Proben- orientierung grundlegend untersucht. Auf Bariumtitanat, einem mehrdomänigen Kristall, wurden analoge Messungen durchgeführt und zusätzlich Gebiete mit ver- schiedenen Domänensorten abgebildet, wobei ein direkter nachfeldoptischer Kon- trast aufgrund der Anisotropie der Probe nachgewiesen werden konnte. Die experimentellen Ergebnisse dieser Arbeit stimmen mit den theoretischen Vorhersagen überein. Ein durch die optische Anisotropie der Probe induzierter Nahfeldkontrast ist messbar und erlaubt die optische Unterscheidung von Gebie- ten mit unterschiedlicher Orientierung des Dielektriziätstensors, wobei eine Än- derung desselben sowohl parallel als auch senkrecht zur Probenoberfläche messbar ist. Diese Methode erlaubt die hochauflösende optische Untersuchung von lokalen Anisotropien, was in zahlreichen Gebieten der Materialwissenschaft, Speichertech- nik, Biologie und Nanooptik von Interesse ist
11
Stevenson, Richard. "Scanning near-field optical microscopy (SNOM) of semiconductor nanostructures." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621756.
Full text
12
Chaipiboonwong, Tipsuda. "Characterising nonlinear waveguides by scanning near-field optical microscopy." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/65528/.
Full textAbstract:
Scanning near-field optical microscopy (SNOM) has been applied to investigate the dispersion and nonlinear phenomena in a multimode Ta2O5 rectangular waveguide. Unlike the conventional approach of observing only the output spectra, the SNOM technique can collect the localised spectra from the evanescent field at various locations of the waveguide. This provides the visualisation of pulse evolution prior to the final development as the output light. The SNOM-acquired spectra consist of unique features which have not been observed before in previous nonlinear pulse propagation researches. These distinctive characteristics are attributed to the localised nature of the data and the multimode nonlinear pulse propagation. In order to understand the underlying physics of the experimental data, a numerical model simulating this SNOM visualisation has been developed. The simulation was based on the nonlinear Schrödinger equation, adapted for multimode pulses, and performed by the split-step Fourier algorithm. The spectra exhibit very fine features which can be attributed to the interference of various modes with different phase modulation owing to dispersion and nonlinear effects. Accordingly, the complexity of the spectral features increase with the propagation distance and the number of contributing modes. The multimode spectra rapidly broaden at the beginning stage of the propagation, owing to the supplementary intermodal phase modulation. Unlike the single-mode case, in which the spectral broadening caused by the self-phase modulation continuously develops along the propagation distance, the broadening process in the multimode pulse is decelerated at the later distance. This is owing to the separation of the higher-order modes and consequently the influence of the cross-phase modulation on the spectral broadening is reduced. The SNOM technique can also provide the observation of high resolution evolution of the pulse spectra. Both spectral variations along the length of the waveguide and across the waveguide are observable. Such a variation over the wavelength scale is caused by the interference of modes with different phases complexly formed by the dispersion and nonlinear effects.
13
Menasche, David. "Error Analysis of Near-Field High Energy Diffraction Microscopy." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/995.
Full textAbstract:
Among non-destructive characterization techniques able to probe the properties of bulk polycrystals, High Energy Diffraction Microscopy (HEDM) has become the method of choice for researchers seeking spatial resolution of grain orientations and strain states. From HEDM data collected in the near field, the forward modeling method (FMM) of reconstruction is capable of producing micro-scale resolution of the orientation field, despite complex grain morphologies and significant plastic strains. In this thesis, the accuracy of the FMM reconstruction is examined through direct comparison with an Electron Backscatter Diffraction (EBSD) measurement of a pure gold specimen. The sensitivity of the FMM reconstruction to its inputs is probed through a series of simulations. Given raw diffraction data collected under optimum experimental conditions, spatial resolution is found to be accurate to within intrinsic limits set by the experimental equipment. Resolution of reconstructed crystallographic orientations is found to be <0:05o. Input parameters most likely to cause reconstruction errors are identified, and a novel method is proposed to determine proper values for experimental inputs. Two case studies are also presented.
14
Low, Chun Hong. "Near Field Scanning Optical Microscopy(NSOM) of nano devices." Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Dec/08Dec%5FLow.pdf.
Full textAbstract:
Thesis (M.S. in Combat Systems Science and Technology)--Naval Postgraduate School, December 2008.Thesis Advisor(s): Haegel, Nancy M. ; Luscombe, James. "December 2008." Description based on title screen as viewed on January 29, 2009. Sponsoring/Monitoring Agency Report Number: "DMR-0526330." Includes bibliographical references (p. 59-61). Also available in print.
15
Morrish, Dru, and DruMorrish@gmail com. "Morphology dependent resonance of a microscope and its application in near-field scanning optical microscopy." Swinburne University of Technology. Centre for Micro-Photonics, 2005. http://adt.lib.swin.edu.au./public/adt-VSWT20051124.121838.
Full textAbstract:
In recent times, near-field optical microscopy has received increasing attention for its
ability to obtain high-resolution images beyond the diffraction limit. Near-field optical
microscopy is achieved via the positioning and manipulation of a probe on a scale less
than the wavelength of the incident light.
Despite many variations in the mechanical design of near-field optical microscopes almost all rely on direct mechanical access of a cantilever or a derivative form to probe the sample. This constricts the study to surface examinations in simple sample environments. Distance regulation between the sample surface and the delicate probe
requires its own feedback mechanism. Determination of feedback is achieved through
monitoring the shift of resonance of one arm of a 'tuning fork', which is caused by the interaction of the probes tip with the Van der Waals force. Van der Waals force emanates from atom-atom interaction at the top of the sample surface. Environmental contamination of the sample surface with additional molecules such as water makes accurate measurement of these forces particularly challenging. The near-field study of
living biological material is extremely difficult as an aqueous environment is required for its extended survival. Probe-sample interactions within an aqueous environment that
result in strong detectable signal is a challenging problem that receives considerable
attention and is a focus of this thesis.
In order to increase the detectible signal a localised field enhancement in the probing region is required. The excitation of an optically resonant probe by morphology dependent resonance (MDR) provides a strong localised field enhancement. Efficient MDR excitation requires important coupling conditions be met, of which the localisation of the incident excitation is a critical factor.
Evanescent coupling by frustrated total internal reflection to a MDR microcavity provides an ideal method for localised excitation. However it has severe drawbacks if the probe is to be manipulated in a scanning process. Tightly focusing the incident illumination by a high numerical aperture objective lens provides the degree of freedom to enable both MDR excitation and remote manipulation. Two-photon nonlinear excitation is shown to couple efficiently to MDR modes due to the high spatial localisation of the incident excitation in three-dimensions. The dependence of incident excitation localisation by high numerical aperture objective on MDR efficiency is thoroughly examined in this thesis. The excitation of MDR can be enhanced by up to 10 times with the localisation of the incident illumination from the centre of the
microcavity to its perimeter.
Illuminating through a high numerical aperture objective enables the remote noninvasive
manipulation of a microcavity probe by laser trapping. The transfer of photon momentum from the reflection and refraction of the trapping beam is sufficient enough to exert piconewtons of force on a trapped particle. This allows the particle to be held and scanned in a predictable fashion in all three-dimensions. Optical trapping
removes the need for invasive mechanical access to the sample surface and provides a means of remote distance regulation between the trapped probe and the sample. The femtosecond pulsed beam utilised in this thesis allows the simultaneous induction of two-photon excitation and laser trapping. It is found in this thesis that a MDR microcavity can be excited and translated in an efficient manner. The application of this technique to laser trapped near-field microscopy and single molecule detection is of particular interest.
Monitoring the response of the MDR signal as it is scanned over a sample object enables a near-field image to be built up. As the enhanced evanescent field from the propagation of MDR modes around a microcavity interacts with different parts of the sample, a measurable difference in energy leakage from the cavity modes occurs. The definitive spectral properties of MDR enables a multidimensional approach to imaging and sensing, a focus of this thesis. Examining the spectral modality of the MDR signal
can lead to a contrast enhancement in laser trapped imaging. Observing a single MDR mode during the scanning process can increase the image contrast by up to 1:23 times compared to that of the integrated MDR fluorescence spectrum.
The work presented in this thesis leads to the possibility of two-photon fluorescence
excitation of MDR in combination with laser trapping becoming a valuable tool in near-
field imaging, sensing and single molecule detection in vivo. It has been demonstrated
that particle scanned, two-photon fluorescence excitation of MDR, by laser trapping 'tweezers' can provide a contrast enhancement and multiple imaging modalities. The spectral imaging modality has particular benefits for image contrast enhancements.
16
Doughty, Jeffrey Jon. "Symmetric Near-Field Probe Design and Comparison to Asymmetric Probes." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/390.
Full textAbstract:
Tip Enhanced Near-field Optical Microscopy (TENOM) is a method for optically imaging at resolutions far below the diffraction limit. This technique requires optical nano-probes with very specialized geometries, in order to obtain large, localized enhancements of the electromagnetic field, which is the driver behind this imaging method. Traditional methods for the fabrication of these nano-probes involve electrochemical etching and subsequent FIB milling. However, this milling process is non-trivial, requiring multiple cuts on each probe. This requires multiple rotations of the probe within the FIB system, which may not be possible in all systems, meaning the sample must be removed from vacuum, rotated by hand and placed back under vacuum. This is time consuming and costly and presents a problem with reproducibility. The method presented here is to replace multiple cuts from a side profile with a small number of cuts from a top down profile. This method uses the inherent imaging characteristics of the FIB, by assigning beam dwell times to specific locations on the sample, through the use of bitmap images. These bitmaps are placed over the sample while imaging and provide a lookup table for the beam while milling. These images are grayscale with the color of each pixel representing the dwell time at that pixel. This technique, combined with grayscale gradients, can provide probes with a symmetric geometry, making the system polarization independent.
17
Kershaw, Kevin Neil. "Development of scanning near-field optical microscopy for biological applications." Thesis, University of Leeds, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405591.
Full text
18
Demming, Anna Linda. "Theoretical investigations into apertureless scanning near field optical microscopy systems." Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429644.
Full text
19
Milner, Robert George. "Scanning near field optical microscopy : aperture experiments and apertureless theory." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620218.
Full text
20
SHARMA, ADITI. "A NEAR FIELD SCANNING OPTICAL MICROSCOPY INVESTIGATION OF PHOTONIC STRUCTURES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1046725704.
Full text
21
Mannelquist, Anders. "Near-field scanning optical microscopy and fractal characterization with atomic force microscopy and other methods /." Luleå, 2000. http://epubl.luth.se/1402-1544/2000/40/index.html.
Full text
22
Jacob, Rainer. "Scanning near-field infrared microspectroscopy on semiconductor structures." Helmholtz-Zentrum Dresden-Rossendorf, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-85330.
Full textAbstract:
Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source.
In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems.
In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from literature. While the structures of the first system were in the micrometer regime, the capability to probe buried nanostructures is demonstrated at a sample of indium arsenide quantum dots. Those dots are covered by a thick layer of gallium arsenide. For the first time ever, it is shown experimentally that transitions between electron states in single quantum dots can be investigated by near-field microscopy. By monitoring the near-field response of these quantum dots while scanning the wavelength of the incident light beam, it was possible to obtain characteristic near-field signatures of single dots. Near-field contrasts up to 30 % could be measured for resonant excitation of electrons in the conduction band of the indium arsenide dots.
23
Varghese, Smitha. "Characterisation of near-field optical trapping and biological applications." Swinburne Research Bank, 2007. http://hdl.handle.net/1959.3/22585.
Full textAbstract:
Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2007.A thesis submitted for the degree of Doctor of Philosophy, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2007. Typescript. Bibliography: p. 135-153.
24
Deutsch, Bradley M. "Phase-Shifting Interferometry for Near-Field Optical Microscopy and Nanoparticle Detection." UNIVERSITY OF ROCHESTER, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3498230.
Full text
25
Cordoba, Erazo Maria Fernanda. "Near-field Microwave Microscopy for Surface and Subsurface Characterization of Materials." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5930.
Full textAbstract:
This dissertation presents an investigation on the capabilities of Near-Field Microwave Microscopy (NFMM) for the characterization of surface and subsurface materials. Subsurface characterization refers to the detection, differentiation and imaging of dielectric, and metallic features that are coated with an insulating layer. The design, simulation and modeling, and testing of a dielectric resonator (DR)-based NFMM and a coaxial transmission line resonator-based NFMM are discussed in detail in this work. Additionally, materials differentiation and imaging capabilities of each microscope are examined using several bulk samples, liquids, GaAs MMIC circuits, and gold/glass testing patterns.
The 5.7 GHz DR-based NFMM uses a microwave probe that consists of a commercial gold-coated probe tip coupled to a DR through a non-resonant microstrip line. The probe is enclosed in an aluminum cavity to preserve the quality factor of the probe (Q=986) and therefore to enhance its sensitivity. The development of a lumped-element model of this DR-based probe is discussed in this work. Characteristics of this design are its high Q and the ability to resolve differences in permittivity (E’r) of insulting bulk samples and liquids as small as ∆E’r =1.75 and ∆E’r =0.04, respectively. The imaging capabilities of this design were verified using a GaAs MMIC phase shifter. It was found that a 10 um wide microstrip line is successfully resolved and that the spatial resolution of the microscope is 50 um when using a tungsten tip with an apex radius of 25 um. Additionally, measurement of the electrical resistance of an additive manufactured resistor was measured using the DR-based NFMM without the need of contacts. The percent difference between the electrical resistance measured using the DR-based NFMM and a four-point probe is 9.6%. Furthermore, the DR-based NFMM allows simultaneous imaging of topography and RF electrical conductivity of rough thick films without the need of an additional distance sensor; this ability is demonstrated for a rough CB028 thick film.
The 5GHz coaxial resonator transmission line-based NFMM employs a half-wavelength coaxial transmission line resonator terminated in a sharp tungsten tip as the microwave probe. A quartz-tuning fork based distance following feedback system is integrated with the microwave probe in order for the NFMM to operate in non-contact mode. The Q of the probe is degraded by 30% (Q=55) due to the presence of the quartz tuning fork. Despite the low Q, this NFMM is able to differentiate several insulating bulk samples (3.8 < E’r < 25) even if they are coated with an insulating layer of thickness similar to the apex radius of the tungsten tip. Finally, the coaxial resonator transmission line-based NFMM is able to image subsurface permittivity distribution of a flexible polymer-composite PDMS-Ba0.55Sr0.45TiO3 49% which is coated with 10 um thick parylene-C layer. Measurements performed at a tip-sample distance of 100 nm reveal that within an area of 50 um x 50 um, the relative permittivity of the polymer-composite is not constant but varies between 6.63 and 11.78.
26
Fenwick, Oliver. "Scanning near-field optical lithography and microscopy of conjugated polymer structures." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1445444/.
Full textAbstract:
This thesis is concerned with the use of the scanning near-field optical microscope (SNOM) to pattern and image conjugated polymer structures. The SNOM is one of just a few optical instruments which are capable of breaking the diffraction limit which limits conventional microscopes to a resolution of approximately half a wavelength. It does so by directing light onto a sub-wavelength aperture at the apex of a probe, establishing a local evanescent field of subwavelength dimensions around the aperture. Conjugated polymers on the other hand are an interesting class of materials which have semiconducting properties and a rich photophysics making them suitable for use in novel light-emitting diodes, transistors and solar cells. I demonstrate direct patterning of several conjugated polymers using the SNOM with a resolution extending below 100 nm and attempt to explain the resolution of the lithography through simulations using the Bethe-Bouwkamp model of the field surrounding a sub-wavelength aperture. In particular the modelling focuses on the role of the film thickness and reflections from the substrate. Further experiments demonstrate that thermal effects which can be caused by heating of the SNOM probe do not play a role in lithography with the SNOM in this case. However, I demonstrate the use of a scanning thermal microscope to do a novel and purely thermal lithography on one of the same conjugated polymers. Resolutions of 120 nm are demonstrated, and finite element analysis is used to show that significant improvements in resolution should be possible by optimisation of the probe and the polymer film. In addition, I present simulations of imaging artefacts caused by topography on samples under SNOM investigation, and use the same model to look at the potential of the SNOM to obtain information about sub-surface objects. SNOM images are presented of blends and supramolecular fibres of conjugated polymers.
27
Venkatesh, Vijay. "Mechanoelectrochemistry of electroactive polymers using shear-force based near-field microscopy." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu158635396991601.
Full text
28
Cvitković, Antonija. "Substrate-enhanced scattering-type scanning near-field infrared microscopy of nanoparticles." München Verl. Dr. Hut, 2009. http://d-nb.info/998908762/04.
Full text
29
Yan, Bing. "A low cost planar near-field / far-field antenna measurement system /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ34242.pdf.
Full text
30
Jia, Baohua. "A study on the complex evanescent focal region of a high numerical aperture objective and its applications." Australasian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20070205.150740/index.html.
Full textAbstract:
Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2005.A thesis submitted for the degree of Doctor of Philosophy, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2005. Typescript. Bibliography: p. 129-142.
31
Yoxall, Edward. "Applications of scattering-type scanning near-field optical microscopy in the infrared." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23637.
Full textAbstract:
This thesis is split into two broad sections. These are defined by the various applications of scattering-type near-field optical microscopy (s-SNOM) in different parts of the electromagnetic spectrum; the near-infrared (700 - 1000nm) and the mid-infrared (6 - 10um). S-SNOM is a means of imaging surfaces at resolutions well below the diffraction limit - the level of recorded detail does not depend on the wavelength of light (as it does with traditional optical microscopy), but instead on the sharpness of a probe (usually around 10nm), meaning an image resolution approaching a thousandth of a wavelength in the mid-infrared. For the work presented in the near-infrared, the focus lies with the modelling and mapping of various plasmonic resonances supported by metallic nanostructures. These resonances have the ability to "squeeze" light into substantially sub-wavelength volumes which is useful for a variety of applications ranging from cancer treatments to molecular sensing. The mid-infrared section starts with the implementation of a pulsed quantum cascade laser (QCL) as the system's light source. This presents some instrumentation challenges as all s-SNOM imaging to date has been conducted with continuous-wave (CW) lasers. Using a pulsed laser also raises some significant signal-to-noise implications which are quantified and discussed. In terms of the experimental applications of such a setup, the first steps towards ultra-high resolution infrared chemical spectroscopy are made by studying the epithelial cells of an oesophageal biopsy. The thesis concludes with an examination of the major noise sources faced by s-SNOM, and makes a number of recommendations on how their effects can be mitigated.
32
Berry, Sam. "Ultra-high spatial and temporal resolution using Scanning Near-field Optical Microscopy." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/348102/.
Full textAbstract:
Scanning near-field optical microscopy (SNOM) is a system that can image beyond the conventional diffraction limit. It does this by collecting the information contained within evanescent fields. This unique ability to image using evanescent fields also enables SNOM to directly measure the electric field distribution in waveguides, where light is guided by total internal reflection. When SNOM is used with a spectrally resolving detector, local temporal phenomena can be detected by analysing spectral interference in the spectra collected by the probe. This spectrally resolving configuration was used to directly measure inter-modal group velocity difference in a multimode ridge waveguide and, using the modes’ spatial profiles to experimentally determine the mode amplitude coefficient ratio. Such an ability to provide measurements on the local dispersion characteristics and relative modal amplitudes of guided light establishes SNOM as a route for investigating the conversion of current single mode photonic devices into multimode devices. The spectrally resolving SNOM system was also used to investigate the sources of temporal delays created by a quasi disordered scattering sample, which was based on John H. Conway’s pinwheel tiling. Whilst the measurements do not create a complete picture of the scattering phenomena in this work, suggestions for improvement are offered with the aim establishing spectrally resolving SNOM systems as tools for mapping localised temporal phenomena in disordered scattering systems.
33
Hall, Jeffrey E. "Exploring photorefractive polymer-dispersed liquid crystals using near-field scanning optical microscopy /." Search for this dissertation online, 2004. http://wwwlib.umi.com/cr/ksu/main.
Full text
34
Gu, Sijia. "Contribution to broadband local characterization of materials by near-field microwave microscopy." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10175/document.
Full textAbstract:
Les microscopes champ proche micro-ondes sont des instruments émergents pour la caractérisation de matériaux. Dans ce travail, un microscope champ proche micro-ondes fait maison est d'abord décrit et analysé en termes de résolution et de largeur de bande de fréquences de fonctionnement. Ensuite, il est mis en œuvre pour la caractérisation d'une grande variété de matériaux tels que par exemple des métaux, des semi-conducteurs, des diélectriques, des liquides et des nanomatériaux 2D. Le système intégre un interférométre pour améliorer la sensibilité de la mesure pour des fréquences de fonctionnement couvrant la bande 2-18 GHz. La sensibilité et les différents modes de fonctionnement disponibles (contact, sans contact, environnement liquide) permettent d'adresser une grande variété de domaines d'applications. La résolution latérale obtenue par cet instrument est plus petite de plusieurs ordres de grandeur que la longueur d'onde de fonctionnement, ouvrant ainsi la voie à une caractérisation locale. Les propriétés électromagnétiques des matériaux ont été extraites en utilisant la méthode de perturbation et celle de la ligne de transmission. En particulier, les propriétés diélectriques de solutions salines aqueuses et l’impédance complexe du graphène ont été étudiées dans une large bande de fréquence. Ce microscope champ proche micro-ondes basé sur une méthode interférométrique qui permet une analyse quantitative des propriétés des matériaux de manière non-destructive peut adresser un grand éventail d’applications dans de nombreux domaines scientifiques. Enfin, l’ensemble des résultats montre que potentiellement la microscopie champ proche micro-ondes dispose des atouts pour devenir un outil de métrologie important pour la caractérisation en micro- et nano-électroniqueNear-field microwave microscopes are emerging instruments for materials characterization. In this work, a home-made near-field microwave microscope is first described and analyzed in terms of resolution performance and frequency band of operation. Then, it is applied to the characterization of a large variety of materials such as metals, semiconductors, dielectrics, liquids and 2D nanomaterials. The system is based on an interferometric technique to improve the measurement sensitivity in the entire frequency range of operation spanning from 2 to 18 GHz. The sensitivity and the different operating modes available (contact, non-contact, liquid environment) allow addressing a large variety of application fields. The instrument allows a sub-wavelength lateral resolution which is more than two orders of magnitude smaller than the operating wavelength, opening the way to a local characterization. The cavity perturbation and transmission line approaches have been used to extract the electromagnetic properties of materials. In particular dielectric properties of saline aqueous solutions and complex impedance of graphene have been investigated in a broad frequency band. It provides a quantitative analysis of material properties in a non-destructive manner to address numerous applications in many scientific fields. Finally, all the results together show that the interferometer-based near-field microwave microscope has the potential to become an important metrology tool for characterizations in micro- and nano-electronics
35
Quartel, John Conrad. "A study of near-field optical imaging using an infrared microscope." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313413.
Full text
36
Xiao, Zhizhao. "Optical properties of zinc oxide nanostructure materials using near-field scanning optical microscopy /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202007%20XIAO.
Full text
37
Teetsov, Julie Ann. "Photophysical characterization and near-field scanning optical microscopy of dilute solutions and ordered films of alkyl-substituted polyfluorenes /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004384.
Full text
38
Nowak, Derek Brant. "The Design of a Novel Tip Enhanced Near-field Scanning Probe Microscope for Ultra-High Resolution Optical Imaging." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/361.
Full textAbstract:
Traditional light microscopy suffers from the diffraction limit, which limits the spatial resolution to λ/2. The current trend in optical microscopy is the development of techniques to bypass the diffraction limit. Resolutions below 40 nm will make it possible to probe biological systems by imaging the interactions between single molecules and cell membranes. These resolutions will allow for the development of improved drug delivery mechanisms by increasing our understanding of how chemical communication within a cell occurs. The materials sciences would also benefit from these high resolutions. Nanomaterials can be analyzed with Raman spectroscopy for molecular and atomic bond information, or with fluorescence response to determine bulk optical properties with tens of nanometer resolution. Near-field optical microscopy is one of the current techniques, which allows for imaging at resolutions beyond the diffraction limit. Using a combination of a shear force microscope (SFM) and an inverted optical microscope, spectroscopic resolutions below 20 nm have been demonstrated. One technique, in particular, has been named tip enhanced near-field optical microscopy (TENOM). The key to this technique is the use of solid metal probes, which are illuminated in the far field by the excitation wavelength of interest. These probes are custom-designed using finite difference time domain (FDTD) modeling techniques, then fabricated with the use of a focused ion beam (FIB) microscope. The measure of the quality of probe design is based directly on the field enhancement obtainable. The greater the field enhancement of the probe, the more the ratio of near-field to far-field background contribution will increase. The elimination of the far-field signal by a decrease of illumination power will provide the best signal-to-noise ratio in the near-field images. Furthermore, a design that facilitates the delocalization of the near-field imaging from the far-field will be beneficial. Developed is a novel microscope design that employs two-photon non-linear excitation to allow the imaging of the fluorescence from almost any visible fluorophore at resolutions below 30 nm without changing filters or excitation wavelength. The ability of the microscope to image samples at atmospheric pressure, room temperature, and in solution makes it a very promising tool for the biological and materials science communities. The microscope demonstrates the ability to image topographical, optical, and electronic state information for single-molecule identification. A single computer, simple custom control circuits, field programmable gate array (FPGA) data acquisition, and a simplified custom optical system controls the microscope are thoroughly outlined and documented. This versatility enables the end user to custom-design experiments from confocal far-field single molecule imaging to high resolution scanning probe microscopy imaging. Presented are the current capabilities of the microscope, most importantly, high-resolution near-field images of J-aggregates with PIC dye. Single molecules of Rhodamine 6G dye and quantum dots imaged in the far-field are presented to demonstrate the sensitivity of the microscope. A comparison is made with the use of a mode-locked 50 fs pulsed laser source verses a continuous wave laser source on single molecules and J-aggregates in the near-field and far-field. Integration of an intensified CCD camera with a high-resolution monochromator allows for spectral information about the sample. The system will be disseminated as an open system design.
39
Inglis, William. "Investigating probe-sample interactions in NSOM." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288999.
Full text
40
Hodges, Christopher Sean. "Theory and practice of near-field thermal probes for microscopy and thermal analysis." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322519.
Full text
41
Williamson, Ricky Lawrence. "Near-field optical and shear force microscopy : instrument development, theoretical background and applications." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296690.
Full text
42
Froehlich, Fred Franklin. "Optical contrast mechanisms and shear force interactions in near-field scanning optical microscopy." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/187486.
Full textAbstract:
This dissertation investigates mechanisms that influence image formation in near-field scanning optical microscopy (NSOM) performed with tapered fiber aperture probes. Both the generation of optical contrast for transmission mode NSOM and the force interaction between the probe and sample that is the basis for topographic imaging by shear force microscopy (SFM) are studied. A brief introduction and review of the field of NSOM are given. The lack of understanding in the previous work of the optical and force interactions between the probe and sample is cited as the motivation for the present investigation. A theoretical model is developed that describes the linear scattering of the probe's source field by the complex transmittance of the sample. The imaging of subwavelength features is shown to arise from the spatial mixing of the evanescent waves of the probe's source field with the high spatial frequencies of the object. Calculations of the optical transfer function are presented. The shear force servo that regulates the probe-to-sample separation and facilitates the acquisition of SFM imagery is extensively analyzed. The optical detection scheme that measures the dither vibration of the probe is characterized in order to optimize the servo performance. The shear force interaction is then analyzed by modeling the probe as a simple harmonic oscillator. Measurements of the probe's resonant response while interacting with the sample reveal that the shear force is mainly frictional. The magnitude of the force is derived, and limitations on its measurement are established through analysis of the minimum detectable displacement of the probe. The servo performance is shown to be shot noise limited, as opposed to being limited by the thermal vibration noise of the probe. Experimental SFM and NSOM images of various grating structures and optical data storage materials are presented. The optical contrast mechanisms displayed in the images are identified. Linear scattering generally dominates the contrast, but some images exhibit unique near-field effects due to probe-sample interactions that lead to nonlinear imaging behavior. The origin of these interactions is the boundary conditions imposed on the probe's aperture by the sample's composition and structure.
43
Lucchesi, Christophe. "Design and development of a near-field thermophotovoltaic conversion device." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI053.
Full textAbstract:
Une cellule thermophotovoltaïque (TPV) convertit l’énergie de photons émis par des corps chauds en énergie électrique. Lorsque la distance séparant deux corps rayonnants devient inférieure à la longueur d’onde caractéristique du rayonnement thermique (~10 µm à température ambiante, ~2,3 µm vers 1000°C), le transfert de chaleur radiatif peut s’accroître de plusieurs ordres de grandeur grâce à la contribution des ondes évanescentes. Cette propriété a un intérêt pour la récupération d’énergie en promettant une augmentation de la puissance électrique générée par une cellule TPV lorsqu’elle est placée en champ proche d’un émetteur thermique radiatif. Dans le but de vérifier cette prédiction, cette thèse a consisté à développer un banc expérimental de mesures TPV en champ proche. Le dispositif est basé sur un montage de microscopie thermique avec actuateurs piézo-électriques (SThM). L’émetteur est une sphère micrométrique de graphite attachée sur un levier SThM chauffé de manière thermorésistive jusqu’à 1200 K et la cellule TPV en antimoniure d’indium (InSb), qui ne peut fonctionner au-delà de 100 K, est placée sur le doigt froid d’un cryostat. Le flux radiatif en champ proche transféré par l’émetteur peut être mesuré indépendamment de la puissance électrique générée par la cellule. La preuve expérimentale de l’accroissement de la densité de puissance électrique générée en champ proche, par rapport à la prédiction de la théorie macroscopique du rayonnement, a été apportée avec un facteur jusqu’à 6. L’étude de différents paramètres a permis d’atteindre des puissances TPV de 7.5 kW.m-2 et des rendements de conversion mesurés de ~20 %. Des expériences de transfert radiatif en champ proche dans diverses configurations (matériaux, géométries, températures) ont également été menées. La puissance radiative transférée en champ proche suit des lois de puissance très différentes de celles du champ lointain. Ces résultats démontrent expérimentalement l’intérêt applicatif des effets de champ proche pour le rayonnement thermiqueThermophotovoltaic (TPV) cells convert the energy of photons emitted by hot bodies into electrical energy. When the distance between two radiating bodies becomes smaller than the characteristic wavelength of thermal radiation (~ 10 µm at room temperature and ~ 2.3 µm near 1000 °C), radiative heat transfer can be enhanced by several orders of magnitude due to the contribution of evanescent waves. This property has an interest for energy harvesting because it should increase the electrical power generated by a TPV cell located in the near field of a radiative thermal emitter. With the aim of confirming this prediction, this thesis consisted in the development of an experimental setup for performing near-field TPV measurements. The setup is based on a scanning thermal microscopy (SThM) design involving piezoelectric actuators. The emitter is a microsphere made of graphite and glued on a SThM cantilever heated by Joule effect up to 1200 K and the TPV cell made of indium antimonide (InSb), which cannot operate above 100 K, is placed on the cold finger of a cryostat. Near-field radiative heat flux transferred from the emitter is measured independently from the electrical power generated by the cell. A study of different parameters provided the experimental proof of the near-field enhancement of the electrical power density generated in the near field by a factor up to 6 compared with the prediction based on the macroscale theory of thermal radiation. Output electrical power densities reach 7.5 kW.m-2 and conversion efficiencies ~20 %. In addition, near-field radiative heat transfer experiments were performed in various configurations (materials, geometries and temperatures). The near-field radiative power follows power laws different from those of the far field. These results highlight the interest of near-field effects on radiative heat transfer for applications
44
López, Ayón Gabriela. "Applying a commercial atomic force microscope for scanning near-field optical microscopy techniques and investigation of Cell-cell signalling." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=92400.
Full textAbstract:
The field of research of this thesis is Condensed Matter Physics applied to Biology. Specifically it describes the development of different Atomic Force Microscopy techniques and tools towards the study of living cells in physiological solution. Particular interest is put into the understanding of the influence of noise in the determination of ordered liquid layers above a mica surface - as work towards the study of the role of water and ions in biological processes - and the influence of "diving bell" to boost the Q factor and allow stable imaging and force spectroscopy with tips based on Scanning Near-field Optical Microscopy [LeDue, 2010 and LeDue, 2008]. By combining SNOM techniques as a local illumination method (and thus avoiding photo bleaching of individual molecules) and high resolution AFM techniques we will be able to investigate mechano-transduction and associated signaling in living cells and individual proteins.Le domaine de recherche de cette thèse consiste en l'application de la physique de la matière condensée à la biologie. Plus précisément, ce travail décrit le développement de différentes techniques de Microscopie à Force Atomique (MFA) et d'outils permettant l'étude de cellules vivantes en solution physiologique. Un intérêt particulier est porté à la compréhension de l'influence du bruit dans la détermination de couches liquides ordonnées au-dessus d'une surface de mica - en tant que travail préalable à l'étude du rôle de l'eau et des ions dans les processus biologiques - et de l'influence d'une "cloche de plongée" pour renforcer le facteur Q ainsi que pour permettre l'imagerie stable et la spectrométrie de force avec des sondes basées sur la Microscopie Optique en Champ Proche (MOCP). En combinant des techniques MOCP, utilisées comme méthode d'éclairement local (évitant ainsi le photoblanchiment des molécules individuelles), et des techniques MFA haute résolution, nous serons capables d'investir la mécano-transduction et le signalement associé dans des cellules vivantes et dans des protéines individuelles.
45
Jacob, Rainer. "Scanning near-field infrared microspectroscopy on semiconductor structures." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-68317.
Full textAbstract:
Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source. In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems. In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from literature. While the structures of the first system were in the micrometer regime, the capability to probe buried nanostructures is demonstrated at a sample of indium arsenide quantum dots. Those dots are covered by a thick layer of gallium arsenide. For the first time ever, it is shown experimentally that transitions between electron states in single quantum dots can be investigated by near-field microscopy. By monitoring the near-field response of these quantum dots while scanning the wavelength of the incident light beam, it was possible to obtain characteristic near-field signatures of single dots. Near-field contrasts up to 30 % could be measured for resonant excitation of electrons in the conduction band of the indium arsenide dotsDie optische Nahfeldmikroskopie hat viel Beachtung auf sich gezogen, da sie die einzige Technologie ist, welche die Untersuchung lokaler optischer Eigenschaften mit Auflösungen unterhalb der Beugungsgrenze ermöglicht. Speziell die streuende Nahfeldmikroskopie erlaubt die zerstörungsfreie Untersuchung von Oberflächen ohne Einschränkung der verwendbaren Wellenlängen. Die Nutzung ist jedoch durch das Vorhandensein entsprechender Lichtquellen beschränkt. Im Rahmen dieser Arbeit wurde diese Beschränkung durch Entwicklung eines streuenden Nahfeldmikroskops überwunden, das einen weit stimmbaren Freie-Elektronen-Laser als primäre Lichtquelle benutzt. Im theoretischen Teil wird gezeigt, dass ein optischer Kontrast erwartet werden kann, wenn Materialien mit unterschiedlichen Dielektrizitätskonstanten kombiniert werden. Es wird hergeleitet, dass diese Unterschiede in unterschiedlichen Streuquerschnitten für das gekoppelte System aus Messkopf und Probe resultieren. Diese Streuquerschnitte definieren die Stärke des Nahfeldsignals, welches auf unterschiedlichen Materialien gemessen werden kann. Ein optischer Kontrast kann also erwartet werden, wenn unterschiedliche Streuquerschnitte untersucht werden. Dass dieses Prinzip auch auf übereinander geschichtete oder sogar verborgene Strukturen angewendet werden kann, wird in dieser Doktorarbeit an zwei Probensystemen experimentell gezeigt. Im ersten Beispiel wurden die unterschiedlichen Dielektrizitätskonstanten durch örtliches Ändern der Ladungsträgerdichte in Silizium durch Bor-Implantation erreicht. Es wird gezeigt, dass die Dichte der freien Ladungsträger an Hand des optischen Kontrastes zwischen implantiertem und reinem Silizium ermittelt werden kann. Zu diesem Zweck wurden zwei unterschiedliche Ansätze verwendet, ein nicht-interferometrischer mittels variabler Wellenlängen und ein interferometrischer mit einer konstanten Wellenlänge. Weil diese Techniken gegensätzliche Informationen liefern, können sie genutzt werden, um die effektive Ladungsträgerdichte quantitativ zu bestimmen. Beide Ansätze lieferten konsistente Resultate für die Trägerdichte, welche sehr gut mit den Vorhersagen der Literatur übereinstimmt. Während die Strukturen im ersten Beispiel im Mikrometer-Bereich lagen, wird die Möglichkeit, verborgene Nanostrukturen zu untersuchen, an Hand einer Probe mit Indiumarsenid Quantenpunkten demonstriert. Diese sind von einer dicken Schicht Galliumarsenid bedeckt. Zum ersten Mal wird experimentell gezeigt, dass Übergänge zwischen Elektronenzuständen in einzelnen Quantenpunkten mit Nahfeldmikroskopie untersucht werden können. Durch die Messung der Nahfeld-Antwort der Quantenpunkte unter Änderung der Wellenlänge des eingestrahlten Lichtes war es möglich, charakteristische Nahfeld-Signaturen der einzelnen Quantenpunkte zu erhalten. Nahfeld-Kontraste bis zu 30 Prozent konnten für die resonante Anregung der Elektronen im Leitungsband der Indiumarsenid Punkte beobachtet werden
46
Brockman, Theodore Alex. "Shear-Force Acoustic Near-Field Microscopy and Its Implementation in the Study of Confined Mesoscopic Fluids." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4710.
Full textAbstract:
The recently developed Shear-Force Acoustic Near-Field Microscope (SANM) is used to investigate the viscoelastic properties of a mesoscopic fluid layer confined between two trapping boundaries, one being a stationary substrate and the other the apex of a laterally oscillating tapered probe. Hardware improvements and evaluation of the SANM-probe robustness will be a major focus of this thesis. The investigation first discusses characterization and recent developments made to the microscope, including: modifications to the sensor head, conditioning of the Nano positioners electrical drive signal, and the assessment of the probe against eventual plastic deformation or compliance against interactions with samples (the latter comprising a solid substrate and its adhered fluid layer which is typically a few monolayers thick). Furthermore, this study includes an analysis of the adsorbed mesoscopic fluid's viscoelastic properties. This inquiry aims to better understand probe-sample interactions with the mesoscopic fluid. This includes adhesion, wetting, and to inquire the nature of the hydrophobic interaction, which is relevant in many areas of study such a protein folding, and interfacial friction which has wide ranging applications including desalination. This analysis will be performed using a Sheer force microscopy (implemented with quartz tuning fork QTF), and another recently introduced technique Whispering Gallery Acoustic Sensor (WGAS). The latter allows more direct monitoring of the QTF's mechanical displacement. These measurements will be supplemented by simultaneously monitoring the acoustic emission from the mesoscopic fluid under confinement between the probe and the substrate, which will be monitored using the SANM sensor positioned beneath the substrate.
47
Ghenuche, Petru Virgil. "Probing the near-field optical response of plasmon nanostructures with two-photon luminescence microscopy." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/22737.
Full textAbstract:
Esta tesis describe el diseño, la fabricación y la caracterización óptica de sistemas plasmónicos resonantes capaces de confinar y aumentar campos de luz en la escala manométrica. En primer lugar, se utilizaron modelos numéricos 3D para diseñar diferentes geometras de nanoestructuras plasmónicas acopladas, a través del cálculo de la respuesta óptica de su campo lejano y cercano. Sobre la base de estas simulaciones se fabricaron las nanoestructuras por litografía de haz electrónico. Se puso especial énfasis en el aumento de la resolución y la optimización de la reproducibilidad de parámetros críticos como la forma de las partículas y el gap entre ellas. Por último, se empleó espectroscopía de campo lejano combinada con espectroscopía de luminiscencia inducida por dos fotones (TPL) para sondar la respuesta óptica local de las geometrías optimizadas.
Hemos centrado nuestra atención en diferentes tipos de estructuras metálicas: dímeros, antenas con gap, conjuntos finitos de partículas en cadenas y en forma de estrella. Los dímeros tienen una fuerte amplificación del campo en su gap nanométrico por el acoplamiento en campo cercano de sus resonancias plasmonicas dipolares. Análogamente, antenas con gap, formadas por dos barras de oro adyacentes que soportan resonancias multipolares, pueden acoplar de manera eficiente la luz y concentrarla en volúmenes pequeños. Se ha demostrado que cadenas finitas de partículas son buenos candidatos para guiar la luz a través de secciones transversales por debajo de la longitud de onda y aquí demostramos que también se pueden utilizar como nanolentes capaces de concentrar la luz en su extremo. La distribución del campo cercano en conjuntos de partículas de oro en forma de estrella presenta una fuerte dependencia con la polarización del campo incidente que puede ser explotada para dirigirse dinámicamente a nano-objetos.
La espectroscopía de campo lejano de conjuntos de dímeros y de cadenas finitas de partculas se comparó con la espectroscopía de TPL.
Nuestro principal resultado es mostrar que la TPL es preferentemente sensible a los campos locales, permitiendo evaluar características espectrosc ópicas que no podrían resolverse de otro modo. A fin de superar las limitaciones de las medidas de conjuntos, en una segunda etapa se dedicó un considerable esfuerzo a construir y optimizar un montaje óptico para medir la señal de TPL de estructuras únicas. El uso de la micro-espectroscopía de TPL permitió obtener mapas espectrales de los modos de antenas aisladas con resolución espacial.
Como se predijo mediante cálculos, hemos sido capaces de visualizar directamente, en la resonancia, la señal de TPL amplificada dentro del gap. Nuestros resultados muestran cómo las medidas de TPL pueden compararse directamente con la distribución de la cuarta potencia del campo local calculado. Mediante el análisis de la evolución de la señal de TPL en función de la longitud de onda incidente en el gap y en las extremidades de la antena tenemos más conocimiento sobre el mecanismo físico detrás de la resonancia de la antena. Finalmente, la microscopía de TPL se utilizó para sondar el campo cercano para diferentes orientaciones de la polarización lineal incidente sobre los conjuntos de partículas en forma de estrella. Se demuestra que, a diferencia del espectro de dispersión, la distribución de TPL en la estructura depende drásticamente del estado de polarización incidente.
Nuestro estudio aporta una contribución significativa al campo de la óptica de plasmones, proponiendo nuevas geometrías para confinar de manera eficiente los campos ópticos a la escala nanometrica, aportando un profundo conocimiento sobre el uso de micro-espectroscopa de TPL como sonda óptica local. Nuestros resultados tendrán importancia en aplicaciones tales como espectroscopía mejorada, biosensores y la interacción luz-materia, donde se necesita evaluar el campo experimentado por una pequeña cantidad de materia cercana a la nanoestructura.This thesis describes the design, fabrication and the optical characterization of plasmon-resonant systems able to confine and enhance light fields down to the sub-wavelength scale. Extensive 3D numerical modeling was first used to design different geometries of coupled plasmonic nanostructures through the calculation of their far-field and near-field optical response. On the basis of simulations, the nanostructures were fabricated by e-beam lithography and thin film deposition. Special efforts were devoted to increasing the resolution and optimizing the reproducibility of critical parameters such as particle shape and interparticle gaps. Finally, far-field spectroscopy combined with two-photon induced luminescence (TPL) spectroscopy was used to probe the local optical response of the optimized architectures. We focused our attention on different families of structures: metal dimers, bar antennas, finite chains of nanoparticles and star-like particle arrangements. Particle dimers feature strong field enhancements in their sub-wavelength gap due to near-field coupling of their dipolar localized plasmon resonances. Based on the same physics, gap antennas, formed by two adjacent gold bars supporting multipolar resonances can efficiently couple to propagating light and concentrate it into tiny volumes. While finite particle chains were previously shown by other authors to be good candidates to guide light through subwavelength cross-sections, we show here that they can also be used as efficient nanolenses able to concentrate light at their extremity. Finally, the near-field distribution in star-like arrangements of gold nanoparticles exhibits a strong dependence with the incident field polarization which can be exploited for dynamical optical addressing of nano-objects. We have compared the far field spectroscopy of large ensembles of dimers and finite chains to TPL spectroscopy. Our main result is to show that TPL is preferentially sensitive to local fields and that it enables the assessment of spectroscopic features which cannot be resolved otherwise. In order to overcome the limitations of measurements on large ensembles a considerable effort was dedicated to mounting and optimizing an optical set-up enabling TPL measurement of single structures. Using the developed TPL micro-spectroscopy, spatially resolved spectral mode mapping on single resonant gap-antennas was achieved. As predicted by calculations, we were able to directly visualize at resonance the strongly enhanced TPL signal within the gap. Our results show how TPL scans can be directly compared with the convoluted distribution of the fourth power of the calculated local mode field. By monitoring the evolution with the incident wavelength of the TPL signal within the gap and at the antenna extremities we got further insight in the physical mechanism behind the buildup of the antenna’s resonance. Finally, TPL microscopy was used to probe the local fields under different orientations of the incident linear polarization near star-like arrangement of gold disks. It is shown that, unlike the scattering spectrum, the TPL distribution over the structure is found to depend drastically on the incident polarization state. Our study brings a significant contribution to the field of Plasmon optics by proposing novel geometries able to efficiently confine optical fields down to the nanometric scale, but also by providing deep insight into the use of TPL microspectroscopy to probe their local optical response. Our findings are foreseen to be important in applications such as enhanced spectroscopy, bio-sensing and enhanced light-matter interaction, where one needs to assess the actual field experienced by small amounts of matter.
48
Vaccaro, Luciana. "Local probe microscopy on lipid membranes : near field optical imaging and shear force studies /." [S.l.] : [s.n.], 2000. http://library.epfl.ch/theses/?nr=2266.
Full text
49
Kolb, Paul Walter. "Cryogenic near-field scanning optical microscopy : quantum dots, charge-ordered domains, and ferromagnetic nucleation /." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1497.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
50
Ganz, Thomas. "Supercontinuum generation by chirped pulse compression for ultrafast spectroscopy and broadband near-field microscopy." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-148551.
Full text