No description available.

Ce mémoire de thèse s’inscrit dans le développement d’un microscope thermique à sonde locale.Ce système d’imagerie présente deux modes de fonctionnement permettant de déterminer soit unetempérature de surface soit des propriétés thermophysiques de matériaux. Un micro-thermocouplebifilaire a été utilisé comme capteur thermique. Il est peu invasif et permet d’accéder à destempératures de surface sur une large gamme de température. De plus, le microscope offrel’avantage d’être moins sensible à la nature optique des échantillons que les méthodes en champlointain. Dans le but de maitriser le contact entre la sonde et la surface, un résonateur à quartz(diapason) a été utilisé comme capteur de force. Un système d’excitation original basé sur l’effetphoto-thermo-élastique a été mis au point. Le microscope fonctionne donc comme un SThM puisqu’ilpermet d’extraire simultanément des images topographiques et thermiques (régime périodique 2 et3 oméga). En revanche, les résultats obtenus ont permis de mettre en évidence les avantages dumicro-thermocouple en termes de résolutions spatiales topographiques vis-à-vis des techniques àsondes résistives fonctionnant en mode 3 oméga. / This PhD thesis deals with the development of a thermalmicroscope using a local probe. This imagingsystem presents two functioning modes that allow determining either surface temperature or thermalproperties of materials. A micro-wire thermocouple is used as a thermal sensor. It is less invasiveand allows measuring the surface temperature with a large temperature range. Furthermore, themicroscope offers an advantage to be less sensitive to the optical nature of a sample surface thanoptical methods. To control the contact between the probe and the surface, a quartz tuning fork hasbeen used as a force sensor. An original excitation system has been developed based on the photothermaleffect. The microscope works also as a SThM since it permits to extract simultaneouslytopographical and thermal pictures (2 and 3 omega periodical modes). Results underlining themicro-thermocouple advantages, in terms of topographical compared to resistive probe techniquesfunctioning with the 3 omega method, have been obtained.

No description available.

abstract: The accurate and fast determination of organic air pollutants for many applications and studies is critical. Exposure to volatile organic compounds (VOCs) has become an important public health concern, which may induce a lot of health effects such as respiratory irritation, headaches and dizziness. In order to monitor the personal VOCs exposure level at point-of-care, a wearable real time monitor for VOCs detection is necessary. For it to be useful in real world application, it requires low cost, small size and weight, low power consumption, high sensitivity and selectivity. To meet these requirements, a novel mobile device for personal VOCs exposure monitor has been developed. The key sensing element is a disposable molecularly imprinted polymer based quartz tuning fork resonator. The sensor and fabrication protocol are low cost, reproducible and stable. Characterization on the sensing material and device has been done. Comparisons with gold standards in the field such as GC-MS have been conducted. And the device’s functionality and capability have been validated in field tests, proving that it’s a great tool for VOCs monitoring under different scenarios. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2017

[pt] A caracterização de cristais osciladores de quartzo (QTF) foi realizada nesta dissertação com o objetivo de implementá–los como sensores de um microscópio de força atômica (AFM). O QTF possui várias vantagens em relação aos cantilevers tradicionais de silício. Utilizado em modos dinâmicos de operação do AFM, o QTF possui maior fator de qualidade e rigidez, permitindo melhor sensibilidade em força e o uso de baixas amplitudes de oscilação para imageamento do que cantilevers tradicionais. Nesse trabalho, parâmetros mecânicos e elétricos do QTF foram medidos. Além disto, um estudo da influência da adição de massa nos braços do QTF foi realizado. Para a implementação do QTF no AFM, um sistema de feedback composto de um amplificador lock–in e um amplificador diferencial foi desenvolvido e testado. Adicionalmente, um novo cabeçote para o microscópio foi desenvolvido para adaptar o QTF ao microscópio. / [en] The characterization of quartz tuning forks (QTF) was performed in this dissertation, aiming to implement them as sensors at an atomic force microscope (AFM). The QTF has several advantages over traditional silicon cantilevers. Used in dynamic AFM modes, the QTF has higher quality factor and stiffness, allowing better force sensitivity and lower amplitudes of oscillation for imaging than traditional cantilevers. In this work, electrical and mechanical parameters of the QTF were obtained. Furthermore, a study of the influence of additional mass on the QTF prongs was performed. To implement the QTF at the AFM, a feedback system composed of a lock–in amplifier and a differential amplifier was developed and tested. Additionally, a new microscope head was designed to adapt the QTF to the microscope.

Organic and inorganic nanostructured materials, nano- and mesoscale objects and devices, and their integration into existing microelectronic technologies have been at the center of recent fundamental and applied research in nanotechnology. One of the critical needs is to develop an enhanced predictive capability of structure-property correlations and enable robust high performance systems by design. My thesis work was concerned with the theoretical and experimental studies of electronic and mechanical properties of chemically functionalized nanowires. I will describe a theoretical approach for investigating structure-property correlations in atomic-sized metallic wires based on the Density Functional Theory (DFT) for structure calculations and the Non-equilibrium Green's Function (NEGF) technique for electronic transport properties simulations. This synergistic approach is shown to yield the atomic structure of the smallest niobium nanowires. Furthermore, the method was applied to simulate electronic properties of chemically functionalized graphene nanoribbons. Further, I will demonstrate an experimental technique for simultaneous measurements of force and conductance in atomic-size objects based on quartz tuning fork piezoelectric sensors. A peculiar scaling effect, relevant for a broad range of test and measurement applications, namely the squeeze film effect, was observed during the development of the sensors. Using theoretical analysis based on finite element simulations of the hydrodynamic behavior of the sensors in a broad range of ambient conditions, I explain the observed phenomenon.

Orientador: Daniel Mario Ugarte / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-15T02:39:35Z (GMT). No. of bitstreams: 1 Oiko_VitorToshiyukiAbrao_M.pdf: 7596860 bytes, checksum: c9ed7c1eff25bf830795b90b88bdc6fa (MD5) Previous issue date: 2010 / Resumo: O estudo de nano-sistemas tem atraído grande atenção nos últimos anos, principalmente devido às suas possíveis e novas aplicações tecnológicas. Muitos esforços têm sido feitos nessa área, porém há ainda várias questões em aberto com relação à compreensão de nanoestruturas. Um dos principais desafios diz respeito à manipulação e o posicionamento controlado de nano-objetos, juntamente com a quantificação das forças envolvidas e a caracterização das propriedades mecânicas em nanoescala. Muitos avanços foram atingidos com a combinação de técnicas de microscopia de força atômica (AFM). Infelizmente nestes experimentos o sensor de forças também é utilizado para gerar uma imagem da amostra. Assim não é possível visualizar o nano-sistema ao mesmo tempo em que ele é submetido a algum esforço mecânico. Outros experimentos são realizados in situ em microscópios eletrônicos onde são utilizados porta-amostras especiais com sensores de força de microscópios de AFM.Combina-se dessa forma a capacidade de se observar diretamente o nano-sistema com a de aplicar e medir forças em sistemas nanométricos. Nesta dissertação é estudada então uma alternativa para a fabricação de um sensor de forças baseado no uso de diapasões de quartzo (tuning forks). Esse sensor deverá ser utilizado em experimentos de nanomanipulação. Este projeto abordou todos os aspectos necessários à instrumentação, desenho, construção e implementação do sensor. O sensor foi acoplado a um nanomanipulador que opera dentro de um microscópio eletrônico de varredura de alta resolução. Com essa montagem, realizaram-se experimentos preliminares de manipulação e deformação de nanofios semicondutores (InP, de alguns mícrons de comprimento, e de 50-200 nm de diamêtro). As forças foram quantificadas baseando-se nas imagens de microscopia dos fios sendo deformados e utilizando um modelo teórico de deformações elásticas. Esses valores foram correlacionados com as variações das curvas de ressonância do tuning fork, para finalmente obter a calibração do sensor de forças. O sistema permite medir forças com uma sensibilidade de 0:5m N baseando-se somente nas mudanças dos sinais elétricos utilizados para alimentar o diapasão de quartzo / Abstract: The study of nanosystems has attracted great attention in recent years, mainly due to their novel possible technological applications. Many efforts have been made in this area, however there are still several open questions concerning the comprehension of such systems. One of the biggest challenges is the manipulation and the controlled positioning of nano-objects, together with the quantification of the forces involved and the mechanical characterization at the nanoscale. Many advances have been achieved with the combination of atomic force microscopy (AFM) techniques. Unfortunately, in these experiments the force sensor is also applied to generate the sample's images. It doesn't allow the system's visualization simultaneously with the stress application. Other experiments are performed in situ electron microscopes where special sample-holders with AFM cantilevers are used. It combines then the ability of observing the nanosystem directly to the possibility of applying and measuring forces in nanometric scale. In this dissertation it is studied an alternative to the fabrication of a force sensor based on quartz tuning forks. This sensor will be used on nanomanipulation experiments. The project covered all the aspects necessary to the sensor's instrumentation, design, construction and implementation. The sensor was attached to a nanomanipulator that operates inside a high resolution scanning electron microscope. Semiconductor nanowires (InP, a few microns in length and 50-200nm in diameter) were manipulated and deformed with this experimental setup. The force quantification was based on microscopy images of the deformed nanowires and on theoretical model of elastic deformations. The force values were correlated with the variations of tuning fork's resonant curves in order to obtain a calibration curve for the sensor. Sensitivity of 0:5m N were achieved based only on changes on electrical signals fed to the quartz tuning fork / Mestrado / Física da Matéria Condensada / Mestre em Física

Orientadores: Daniel Mario Ugarte, Varlei Rodrigues / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-24T10:25:30Z (GMT). No. of bitstreams: 1 Oiko_VitorToshiyukiAbrao_D.pdf: 44112591 bytes, checksum: 93cb68b7fac3caf690848f58147ff259 (MD5) Previous issue date: 2014 / Resumo: O estudo de nano-sistemas tem atraído grande atenção nos últimos anos, principalmente devido às suas possíveis e novas aplicações tecnológicas. Muitos esforços tem sido feitos nessa área, porém há ainda várias questões em aberto com relação a compreensão de nanoestruturas. Um dos principais desafios diz respeito à manipulação e o posicionamento controlado de nanoobjetos, juntamente com a quantificação das forças envolvidas e a caracterização das propriedades mecânicas em nanoescala. Muitos avanços foram atingidos combinando-se a microscopia eletrônica de varredura (SEM) e a de força atômica (AFM), realizando experimentos in situ que aproveitam a resolução e a formação de imagens do SEM, e a capacidade de medir forças em sistemas nanométricos do AFM. Nesta tese discutimos a quantificação de forças de intensidade < N, aplicadas em experimentos de nanomanipulação in situ de SEM, através do desenvolvimento de um sensor baseado no uso de diapasões de quartzo (tuning fork). Abordamos os aspectos técnicos relevantes à construção do sensor e seu funcionamento, desde o problema de se medir forças da ordem de nN em nano-objetos individuais, até sua aplicação em sistemas dessa dimensão. Pontos fundamentais do desenvolvimento como a definição da sua configuração, da eletrônica de aquisição e da metodologia de calibração e de aplicação são tratados em detalhe. Um processo de calibração baseado na deformação in situ de cantilevers de AFM é utilizado para permitir a quantificação da força. Subsequentemente a medida dos valores é feita exclusivamente através das curvas de ressonância do tuning fork, independendo completamente das imagens de microscopia. Forças no intervalo de 1-100 nN foram medidas, e a aplicação do sensor foi dada no intervalo de 4-40 nN. A precisão obtida na quantificação foi de alguns nN, ?F ?1-4 nN. O sistema foi testado em experimentos de deformação de bundles de nanotubos de carbono in situ em um SEM, nos quais medimos quantitativamente a influência das forças de van der Waals no atrito dinâmico durante o escorregamento entre nanotubos. As forças obtidas nesses experimentos variaram entre 14-35 nN / Abstract: The study of nanosystems has attracted many attention in recent years, mainly due to their novel possible technological applications. Many efforts have been made in this area, however several open questions regarding the comprehension of such structures remain. A major challenge concerns the manipulation and the controlled positioning of nano-objects, together with the quantification of the involved forces and the mechanical characterization at the nanoscale. Many advances have been achieved by combining the scanning electron microscopy (SEM) and the atomic force microscope (AFM), conducting thus in situ experiments that profit from SEM¿s resolution and imaging and from AFM¿s ability to measure forces in nanoscale systems. In this thesis we treat the quantification of forces with intensity < N applied during in situ nanomanipulation experiments performed inside a SEM by developing a force sensor based on quartz tuning forks. Our approach comprises the technical aspects relevant to the sensor¿s assembly and its operation, from the issue of measuring forces of the order of nN on individual nano-objects, to its application on nanosystems. Key points of development such as the sensor¿s design, electronics, calibration and applications are described in details. A calibration process based on the in situ bending AFM cantilevers is carried out to enable the force quantification. Subsequently the force measurement is done exclusively by the TF¿s resonance curve, being completely independent of the microscopy images. Forces in the range of 1-100 nN were measured, and the sensor¿s application was considered between 4 nN and 40 nN. The precison acquired was of a few nN, ?F ?1-4 nN. To test the sensor in situ strain experiments were performed on bundles of carbon nanotubes from which we measured quantitatively the van der Waals¿ influence on the dynamic friction during the sliding of adjacent bundles. The forces acquired were then in the range of 14-35 nN / Doutorado / Física / Doutor em Ciências

La mesure des polluants fait l'objet depuis la fin du XXème siècle d'une attention toute particulière pour la préservation de la planète. Les espèces gazeuses, plus précisément le méthane, présent dans le MIR, possède des forces de raies très intenses, ce qui rend la technique plus sensible. La technique de détection de gaz utilisée durant ma thèse est choisie après une large comparaison entre différentes techniques appartenant à la SDLA. Cette technique est la technique QEPAS. Elle a montré depuis son invention en 2002, une grande sensibilité et sélectivité dans le domaine d'analyse de gaz. La source de lumière utilisée dans la QEPAS est une diode laser accordable (laser à SC), ce qui permet de rendre la technique plus sélective, en variant sa longueur d'onde d'émission en fonction du courant injecté et/ou température de régulation, pour se localiser sur une raie souhaitée à détecter. Le détecteur de la QEPAS est le diapason à quartz (QTF). Ce dernier est très sensible à la force minime appliquée par l'onde acoustique, ce qui rend la technique très sensible aux faibles concentrations. Plusieurs étapes de caractérisations sont exigées pour déterminer les caractéristiques de la diode laser et du QTF. Après le choix de la diode laser et du QTF, idéaux pour la spectroscopie, on passe à l'évaluation de la technique QEPAS dans le domaine d'analyse de gaz. Les limites de détection du méthane obtenues avec la technique QEPAS sont 0.8 ppmv et 400 ppbv à 2.3 µm avec un laser à Fabry-Pérot et un laser à cristaux photoniques, respectivement, et 100 ppbv à 3.3 µm avec un laser DFB.Ce travail a permis d'obtenir une technique performante (sensible, sélective, pas cher…), dans le domaine d'analyse de gaz. / The measurement of the pollutants is the subject since the late twentieth century especially in attention to protecting the planet. The gaseous species, specifically methane, present in the MIR, has strengths rays very intense, making the technique more sensitive.The detection technique of gas used during my PhD was chosen after an extensive comparison of different techniques belonging to the SDLA. This technique is the QEPAS technique. It has shown since its invention in 2002, a high sensitivity and selectivity in gas analysis. The light source used in the QEPAS is a tunable diode laser (Laser SC), thus making the technique more selectively, by varying the wavelength of emission as a function of injected current and / or control temperature to be located on a line desired to detect. The detector is QEPAS of quartz tuning fork (QTF). The latter is very sensitive to small force applied by the acoustic wave, which makes the technique very sensitive to low concentrations. Several steps are required characterization to determine the characteristics of the laser diode and the QTF. After choosing the laser diode and the QTF, ideal for spectroscopy, we pass to the evaluation of the technique QEPAS in gas analysis. The detection limits of methane obtained with the technique are QEPAS 0.8 ppmv and 400 ppbv to 2.3 microns with a Fabry-Perot laser and a photonic crystal laser, respectively, and 100 ppbv to 3.3 microns with a DFB laser.This work has provided a powerful technique (sensitive, selective, cheap ...) in gas analysis.

The thesis is focused on development of scanning probe microscope systems, especially development and implementation of quartz resonator probes. The quartz resonator probes, compared to the standard silicon cantilevers, have several advantages. It is in particular their mechanical properties and possibility of direct electrical readout of the deflection signal. Due to the fact, the probes are easy to implement even into more complex SPM systems. The thesis deals with development of universal and open SPM control system electronics. The electronics consist of the commercial SPM control and oscillation units, the development of the other electronic parts (such as the high voltage amplifier and the preamplifier units) is described in the thesis. Further, the thesis reports on development of the qPlus UHV LT SPM microscope system that was carried out at Universität Hamburg. Part of it was development of the qPlus preamplifier able to operate at liquid helium temperature. The third topic of the thesis is the implementation of qPlus technology into the UHV VT SPM microscope suitable to operate in situ with a scanning electron microscope. The qPlus sensors and the universal UHV preamplifier were designed and manufactured. Test measurements were conducted on all of the developed systems.