Previous research on new novel substrates for giant magnoresistance structures has indicated that a net increase in the effect is present. The substrates studied were V-grooved or stepped, however research presented in this thesis used an embossed surface manufactured from alumina oxide which consisted of regular hexagonal arrays with spacing of 110 nm and pore diameter of 60 nm. The physical properties measurements unveiled a net enhancement of the giant magnetoresistance effect thru the whole range of the copper spacer thicknesses deposited with direct current magnetron sputter. The maximum net increase appeared for a spacer thickness of 4.0 nm where the flat silicon substrate yielded a 3 % increase but the embossed surface substrate generated a 12% increase with an overall effect of a 4-fold net enhancement of the effect. Both the aluminum oxide substrates and the thin films structures can be manufactured inexpensively and can be also mass-produced, which are welcoming advantages for the technology sector of magnetic sensing.

This thesis is an investigation of possible applications for a low cost non-contact magnetic rotational position sensor. A single stage gearbox operating spur gears was instrumented with these sensors along with typical optical encoders. These rotational position devices were used independently to measure gearbox Transmission Error (TE) during operation. Basic filtering techniques were used to condition the TE so that localized faults were observable. Characteristic feature extraction on the TE using RMS, Kurtosis and Crest Factor was used to quantify gearbox dynamics. These features were able to measure dynamic changes in gearbox health, such as wearing in the gears or the progression of a fault resulting in full tooth failure. These sensor attributes are ideal for machine condition monitoring applications where catastrophic failure can be forewarned by incipient fault detection. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2010-10-12 17:21:13.125

While nonlinear behavior in mechanical systems typically degrades the behavior and performance the devices, the presence of system nonlinearities can sometimes improve the quality of the system. A reason for avoiding nonlinearities within a device is the difficulty in controlling the device due to the effects of the nonlinearities on system behavior. However, careful analysis of nonlinear systems can allow for one to take advantage of the nonlinear behavior to improve system performance. The objective of this thesis is to exploit the use of nonlinearities to enhance system performance, specifically the sensitivity of a micromachined magnetic sensor. A device design will be presented that is similar to a prototype that has been fabricated by a student within the Electrical and Computer Engineering Department at Georgia Tech. The operating principle of the device is that changes in the orientation and the strength of an external magnetic field will result in changes in the dynamic behavior of the sensor. While previous device provided a proof of the design concept, it was unable to achieve a sensitivity that would allow for its use as a compass. Improvements in the sensitivity of the sensor are achieved through the modeling and optimization of the magnetic sensor. The optimization and redesign of the magnetic sensor will improve the quality of the device and provide another step towards sensor commercialization. A new design that incorporates the use of variable force comb drives will be proposed that will further improve the sensitivity of the device by modifying the dynamic behavior of the sensor. Another approach that is presented to exploit the nonlinear behavior of the magnetic sensor involves a frequency detection scheme that uses nonlinear vibrations to characterize sensor behavior. Some benefits of this detection technique are that it is insensitive to noise in the vibration of the sensor and is also independent of the damping present within the system. In addition, the implementation of this sensing technique can be readily applied to variety of sensors types without the redesign of a system or the addition of complex components such as vacuum packaging or signal processing electronics.

A micromachined magnetic field sensing system capable of measuring the direction of the Earths magnetic field has been fabricated, measured, and characterized. The system is composed of a micromachined silicon resonator combined with a permanent magnet, excitation and sensing coils, and a magnetic feedback loop. Electromagnetic excitation of the mechanical resonator enables it to operate with very low power consumption and low excitation voltage. The interaction between an external magnetic field surrounding the sensor and the permanent magnet generates a rotating torque on the silicon resonator disc, changing the effective stiffness of the beams and therefore the resonant frequency of the sensor. MEMS-based mechanically-resonant sensors, in which the sensor resonant frequency shifts in response to the measurand, are widely utilized. Such sensors are typically operated in their linear resonant regime. However, substantial improvements in resonant sensor performance can be obtained by designing the sensors to operate far into their nonlinear regime. This effect is illustrated through the use of a magnetically-torqued, rotationally-resonant MEMS platform. Platform structural parameters such as beam width and number of beams are parametrically varied subject to the constraint of constant small-deflection resonant frequency. Nonlinear performance improvement characterization is performed both analytically as well as with Finite Element Method (FEM) simulation, and confirmed with measurement results. These nonlinearity based sensitivity enhancement mechanisms are utilized in the device design. The complete magnetic sensing system consumes less than 200 microwatts of power in continuous operation, and is capable of sensing the direction of the Earths magnetic field. Such low power consumption levels enable continuous magnetic field sensing for portable electronics and potentially wristwatch applications, thereby enabling personal navigation and motion sensing functionalities. A total system power consumption of 138W and a resonator actuation voltage of 4mVpp from the 1.2V power supply have been demonstrated with capability of measuring the direction of the Earths magnetic field. Sensitivities of 0.009, 0.086, and 0.196 [mHz/(Hz and #903;degree)] for the Earths magnetic field were measured for 3, 4, and 6 beam structures, respectively.

In this dissertation, the extraordinary magnetoresistance (EMR) effect in semiconductor/metal hybrid structures is studied to improve the performance in sensing applications. Using two-dimensional finite element simulations, the geometric dependence of the output sensitivity, which is a more relevant parameter for EMR sensors than the magnetoresistance (MR), is studied. The results show that the optimal geometry in this case is different from the geometry reported before, where the MR ratio was optimized. A device consisting of a semiconductor bar with length/width ratio of 5~10 and having only 2 contacts is found to exhibit the highest sensitivity. A newly developed three-dimensional finite element model is employed to investigate parameters that have been neglected with the two dimensional simulations utilized so far, i.e., thickness of metal shunt and arbitrary semiconductor/metal interface. The simulations show the influence of those parameters on the sensitivity is up to 10 %. The model also enables exploring the EMR effect in planar magnetic fields. In case of a bar device, the sensitivity to planar fields is about 15 % to 20 % of the one to perpendicular fields. 5 A “top-contacted” structure is proposed to reduce the complexity of fabrication, where neither patterning of the semiconductor nor precise alignment is required. A comparison of the new structure with a conventionally fabricated device shows that a similar magnetic field resolution of 24 nT/√Hz is obtained. A new 3-contact device is developed improving the poor low-field sensitivity observed in conventional EMR devices, resulting from its parabolic magnetoresistance response. The 3-contact device provides a considerable boost of the low field response by combining the Hall effect with the EMR effect, resulting in an increase of the output sensitivity by 5 times at 0.01 T compared to a 2-contact device. The results of this dissertation provide new insights into the optimization of EMR devices for sensor applications. Two novel concepts are presented, which are promising for realizing EMR devices with high spatial resolution and for opening new applications for EMR sensors in the low-field regime.

Orientador: Carlos Alberto dos Reis Filho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-04T14:40:24Z (GMT). No. of bitstreams: 1 Castaldo_FernandoCardoso_D.pdf: 30688674 bytes, checksum: 38148b8964d0d87ceacc943afb795fbc (MD5) Previous issue date: 2005 / Resumo: Este trabalho aborda a questão da compatibilidade eletromagnética em circuitos chaveados integrados, tipicamente conversores DC-DC dedicados. Neste sentido, propõe-se uma técnica de controle da emissão eletromagnética baseada no sensoriamento do campo magnético próximo através da utilização de transistores MOS do tipo split-drain. Desta forma, pode-se integrar conjuntamente o transistor de potência e o split-drain. O sinal produzido pelo sensor pode ser enviado a um circuito de acionamento que controla a derivada da corrente no transistor de potência, limitando, desta forma, a emissão gerada. Entretanto, o ruído associado ao transistor split-drain limita severamente a resolução do sensor. Estudos realizados indicaram a existência de uma corrente de ruído em excesso observada através de medidas de correlação de ruído, denominada corrente de ruído transversal. Esta corrente limita a relação sinal-ruído do sensor magnético, principalmente no modo diferencial, com impacto direto na resolução do sistema detector. A partir do entendimento dos mecanismos de geração de ruído investigados, circuitos detectores de campo magnético que atendam determinada resolução podem ser projetados, viabilizando-se assim, a implementação de sensores de emissão eletromagnética / Abstract: This work deals with the electromagnetic compatibility (EMI) issues aimed to power integrated circuits, typically DC-DC converters. An EMI controlling approach based on magnetic near field measurements using CMOS split-drain transistors (MAGFETS) as magnetic sensors is investigated. Monolithic applications can be envisaged comprising the power circuit and the magnetic sensor. The detected signal can be sent to a slew-rate-based controlling driver that sets the electromagnetic emissions below a specific leveI. However, the electronic noise associated with the split-drain transistor affects the sensor resolution. In this sense, it was observed through correlation measurements an excess noise current associated with the split-drain transistor, called transversal noise current. A noise model taking into account the transversal noise current is proposed, allowing the implementation of magnetic sensors featuring a specific resolution aimed to electromagnetic emissions detectors / Doutorado / Eletrônica, Microeletrônica e Optoeletrônica / Doutor em Engenharia Elétrica

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-08-02T17:10:41Z No. of bitstreams: 1 Agner Grion_.pdf: 2314653 bytes, checksum: cb04ed0d87d4cb71461f526d2c611f04 (MD5) / Made available in DSpace on 2016-08-02T17:10:41Z (GMT). No. of bitstreams: 1 Agner Grion_.pdf: 2314653 bytes, checksum: cb04ed0d87d4cb71461f526d2c611f04 (MD5) Previous issue date: 2016-06-17 / Nenhuma / Atualmente os sensores magnéticos estão presentes em uma grande variedade de equipamentos, tais como computadores, automóveis, aviões, instrumentos médicos e industriais. Em muitas destas aplicações os sensores magnéticos oferecem meios seguros e não invasivos de detecção e são mais confiáveis do que outras tecnologias. A corrente elétrica em um condutor gera um campo magnético que pode ser detectado por este tipo de sensor. Este trabalho tem como objetivo definir um encapsulamento dedicado a um sensor de corrente elétrica que utiliza uma MTJ (Junção Túnel Magnética) como dispositivo de detecção. No desenvolvimento foram analisadas diferentes propostas de encapsulamentos através do software de modelagem COMSOLR . Os resultados obtidos com a análise térmica, magnética e a avaliação dos custos relativos de produção entre estas propostas levaram a definição de um encapsulamento para a aplicação pretendida. / Nowadays there are magnetic sensors in a wide variety of equipment such as computers, cars, airplanes, medical and industrial instruments. In many of these applications the magnetic sensors offer safe and non-invasive means of detection and are more reliable than others technologies. The electric current in a conductor generates a magnetic field detected by this type of sensor. This work aims to define a package dedicated to an electrical current sensor using a MTJ (Magnetic Tunnel Junction) as a sensing device. Different proposals of packaging were analyzed by COMSOLR modeling software. The results obtained from the thermal and magnetic analysis and the relative costs of production between these proposals led to the definition of a package to the intended application.

The mobile phone devices are still developing and they are gaining more functionality and are able to deal with more advanced tasks. One of the technologies timidly trying to approach the mobile phone market is the augmented reality, which does no longer require external equipment to be formed in a programming application. There is a limited number of sources trying to describe the accuracy of augmented reality applications implemented on mobile devices. Within this study an application of augmented reality visualising virtual models of buildings was implemented on a mobile phone device in order to evaluate the rate of the device explication. Several tests were conducted to evaluate the application total accuracy. The implemented application was visualising virtual models of the real existing buildings displaying them in the same place the original buildings were. The final position was calculated by the application and the discrepancy of the view between the model and the real building was measured. The results were gathered revealing the application’s real accuracy. For the purposes of this study the functional application of augmented reality has been created. The application was implemented on the mobile phone. The results of the application formed the tables with final measurements of accuracy. Also several photographs were taken from the areas of the real existing buildings. Transferring the functionality of augmented reality from the external devices to mobile phones is possible with some harm to the application accuracy. Visualising building models is one of the possible extensions of the mobile phone market. The improvements in Global Positioning System would significantly improve the application´s general accuracy. / The augmented reality represents one of the most current approach in implementing the artificial reality. Primarily required large extensive head-mounted-displays now follows the trend of minimising the necessary equipment. The study shows how is it done that a single mobile phone can be used as a device creating a new reality and also answers what calculations are required by such a system setting the augmented environment. Also a problem of mobile phone’s augmented reality systems accuracy is developed in reference to the commonly proclaimed 2-metres inaccuracy of the GPS device. / (+48) 506 403 407 (PL)

L’objectif des travaux de cette thèse est la réalisation de capteurs magnétiques à ondes élastiques de surface (SAW). Nos études réalisées dans ce cadre se sont focalisées sur la modélisation et la réalisation de dispositifs magnéto-élastique SAW à base de structures multicouches sensibles au champ magnétique. Une géométrie multicouche offrant plusieurs degrés de libertés permettant d’agir sur les performances du capteur a été considérée. La configuration de cette structure est : Substrat piézoélectrique/électrodes interdigitées/Couche isolante/Couche sensible magnéto-élastique. Les différents paramètres de la structure, notamment les épaisseurs des différentes couches et leurs natures ont été optimisées théoriquement au regard du facteur de qualité, du facteur de couplage électromécanique et de la sensibilité au champ magnétique. Des dispositifs utilisant les configurations optimales ont été réalisés et caractérisés et leurs performances comparées au prédiction théoriques. Nous avons montré que le capteur peut être conçu pour répondre aux besoins de l’application en ce qui concerne la gamme de l’intensité du champ à mesurer et de la sensibilité visée. Ainsi le CoFeB utilisé comme couche sensible magnéto-élastique permet une meilleure sensibilité mais sur une étendue étroite du champ magnétique alors que le nickel permet d’étendre la gamme de mesure mais avec moins de sensibilité. Nous avons également montré que l’utilisation comme couche isolante de matériau dur comme l’alumine permet une meilleure sensibilité. Cette sensibilité est également fortement augmentée pour un fonctionnement à hautes fréquences / The aim of this Ph.D. Thesis is to study piezo-magnetic surface acoustic wave (SAW) sensor. Accurate and fully coupled physical model was numerically implemented in order to investigate the sensitivity of SAW devices using the magneto-elastic interaction with an external magnetic field. The different parameters of the structure, including the thicknesses of the various layers and their natures were theoretically optimized with regard to the quality factor, the electromechanical coupling factor and the sensitivity to the magnetic field. Devices using the optimal settings have been made and characterized, and their performance compared to the theoretical prediction. We have shown that the sensor can be designed to meet the needs of the application as regards the range of the field strength to be measured and the target sensitivity. Thus the CoFeB used as magneto-elastic sensitive layer provides better sensitivity but on a narrow stretch of the magnetic field while the nickel expands the measurement range but with less sensitivity. We have also shown that the use of hard material as insulating layer, such as alumina, allows better sensitivity. This sensitivity is also greatly increased when the sensor is operating at high frequencies

Les capteurs magnéto-électrique (ME) sont une alternative prometteuse pour mesurer de faibles signaux magnétiques. Précédemment le choix était généralement de déposer des couches minces magnétostrictives sur un matériau piézoélectrique massif conduisant à des systèmes macroscopiques de taille milllimétrique. L’intégration de ces systèmes dans des MEMS (micro-electro-mechanical systems) requiertà la fois de résoudre les problèmes d’intégration de matériaux actif sur silicium, et de mesurer des petits signaux étant donné l’importante réduction de la réponse du système lorsqu’il est miniaturisé.Dans cette optique, le premier objectif de ce travail de thèse a été d’intégrer un matériau piézoélectrique sur un substrat de silicium tout en conservant une excellente qualité cristalline. Pb(Zr ₀ , ₅ ₂Ti ₀ ,₄₈)O₃ (PZT) a été retenu pour ces excellente propriétés piézoélectriques. L’intégration de la couche mince ce fait sur silicium qui est le substrat de prédilection pour la fabrication de microsystèmes avec les procédés microélectroniques standards. La qualité cristalline des matériaux actifs est directement corrélée aux couches d'adaptation utilisées pour obtenir une bonne qualité cristalline sur silicium. Pour cel l'intégration d'une tricouche composée de zircone stabilisée à l'yttrium (YSZ), d'oxyde de cérium (CeO₂) et de SrTiO₃ permet ensuitela croissance des pérovskites d'intérêt pour le dispositif. Le choix de l’électrode conductrice inférieure (SrRuO₃ ou La ₀ ,₆₆Sr₀₃₃MnO₃ dans le cas présent) permet de contrôler l’orientation de la maille de PZT.Une première étude des propriétés piézoélectriques de la couche mince de PZT sous la forme d’une poutre libre pour son intégration dans un système magnétoélectrique a été réalisé. La mesure de la déformation de la poutre induite par l'application d'une tension électrique permet d'extraire un coefficient d₃₁ de -53pmV⁻¹, valeur inférieure au matériau massif mais à l'état de l'art dans ce type de dispositif. Dans une seconde étape, l’utilisation de la poutre comme résonateur à été étudiée. L’étude dynamique du système a permis d'obtenir la fréquence de résonance et le facteur de qualité. Le déplacement de la fréquence caractéristique du système en fonction d'une contrainte induite par une tension DC a été investigué. Enfin, l'ajout d'une couche de matériau magnétostrictif (TbFeCo) sur la poutre a finalisé la structure du capteur. Le capteur ainsi obtenu a été caractérisé et une sensibilité d’une dizaine de micro Tesla a été obtenue. / Magneto-electric (ME) sensors have been demonstrated as a promising alternative for the detection of weak magnetic signals with high sensitivity. To date, most applications focused on the use of bulk piezoelectric materials on which magnetostrictive thin films are deposited leading to millimeter-sized devices. The integration of such devices into micro-electro-mechanical systems (MEMS), bringing smaller size and lower power consumption, involves addressing several scientific issues ranging from the integration of active materials on silicon to the strong reduction in amplitude of generated signals related to the size reduction of the sensor.In this context, the first goal of this thesis work was to integrate high crystalline quality piezoelectric thin films on silicon.Pb(Zr ₓTi ₁ ₋₁)O₃ (PZT) with a morphotropic composition (x=0.52) having high electromechanical coupling factor was chosen. Silicon is a necessary template as it allows for the use of conventional clean room processes for the realization of the microsystem. The crystalline quality of the active films is directly linked to the buffer layers that promote the crystalline growth on silicon. For this purpose, Yttria-stabilized Zirconia (YSZ) was used in combination with CeO₂ and SrTiO₃ to allow further growth of epitaxial perovskites. The choice of the bottom electrode material (SrRuO₃ or La ₀ ,₆₆Sr₀₃₃MnO₃ in this work) further tunes the crystalline orientation of the PZT layer.To probe the potential of such PZT thin films for ME devices, the first step was to characterize the electromechanical properties of this material in a free standing cantilever structure. Under an applied electric field, the measured displacement of the epitaxial PZT-based cantilevers is characterized by a coefficient d₃₁ =-53pmV⁻¹ , a reduced value with respect to the bulk material but that can be enhanced by further optimizing the film growth. The second step consists in ascertaining the ability of the cantilever to be used as resonator. For that purpose, first characterizations of oscillators have been performed to extract the resonant frequencies and the associated quality factors. Then, the resonant frequency shift with DC bias-induced stress was measured. Finally, a magnetostrictive layer of TbFeCo was added on the PZT cantilevers to sense magnetic field based on the ME effect. The resulting resonant frequency shift with external applied magnetic field was characterized with a typical sensitivity of 10’s of µT.