Rozprawy doktorskie: „MEMS Gas Sensors”

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Gatty, Hithesh K. "MEMS-based electrochemical gas sensors and wafer-level methods". Doctoral thesis, KTH, Mikro- och nanosystemteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172955.

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This thesis describes novel microel ectromechanical system (MEMS) based electrochemical gas sensors and methods of fabrication. This thesis presents the research in two parts. In the first part, a method to handle a thin silicon wafer using an electrochemically active adhesive is described. Handling of a thin silicon wafer is an important issue in 3D-IC manufacturing where through silicon vias (TSVs) is an enabling technology. Thin silicon wafers are flexible and fragile, therefore difficult to handle. In addressing the need for a reliable solution, a method based on an electrochemically active adhesive was developed. In this method, an electrochemically active adhesive was diluted and spin coated on a 100 mm diameter silicon wafer (carrier wafer) on which another silicon wafer (device wafer) was bonded. Device wafer was subjected to post processing fabrication technique such as wafer thinning. Successful debonding of the device wafer was achieved by applying a voltage between the two wafers. In another part of the research, a fabrication process for developing a functional nanoporous material using atomic layer deposition is presented. In order to realize a nanoporous electrode, a nanoporous anodized aluminum oxide (AAO) substrate was used, which was functionalized with very thin layers (~ 10 nm) of platinum (Pt) and aluminum oxide (Al2O3) using atomic layer deposition. Nanoporous material when used as an electrode delivers high sensitivity due to the inherent high surface area and is potentially applicable in fuel cells and in electrochemical sensing. The second part of the thesis addresses the need for a high performance gas sensor that is applicable for asthma monitoring. Asthma is a disease related to the inflammation in the airways of the lungs and is characterized by the presence of nitric oxide gas in the exhaled breath. The gas concentration of above approximately 50 parts-per-billion indicates a likely presence of asthma. A MEMS based electrochemical gas sensor was successfully designed and developed to meet the stringent requirements needed for asthma detection. Furthermore, to enable a hand held asthma measuring instrument, a miniaturized sensor with integrated electrodes and liquid electrolyte was developed. The electrodes were assembled at a wafer-level to demonstrate the feasibility towards a high volume fabrication of the gas sensors. In addition, the designed amperometric gas sensor was successfully tested for hydrogen sulphide concentration, which is a bio marker for bad breath.

QC 20150907

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DeBoer, John Raymond. "Evaluation Methods for Porous Silicon Gas Sensors". Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4971.

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This study investigated the behavior of porous silicon gas sensors under exposure to CO, NO, and NH3 gas at the part per million level. Parameters of interest in this study included the electrical, environmental, and chemi-resistive performance associated with various porous silicon morphologies. Based upon the variability of preliminary results, a gas pulsing method was combined with signal processing in order to analyze small impedance changes in an environment of substantial noise. With this technique, sensors could be effectively screened and characterized. Finally this method was combined with various post-treatments in order to improve the sensitivity and selectivity of individual sensors.

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Zhang, Chen. "Piezoelectric-Based Gas Sensors for Harsh Environment Gas Component Monitoring". Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1538769/.

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In this study, gas sensing systems that are based on piezoelectric smart material and structures are proposed, designed, developed, and tested, which are mainly aimed to address the temperature dependent CO2 gas sensing in a real environment. The state-of-the-art of gas sensing technologies are firstly reviewed and discussed for their pros and cons. The adsorption mechanisms including physisorption and chemisorption are subsequently investigated to characterize and provide solutions to various gas sensors. Particularly, a QCM based gas sensor and a C-axis inclined zigzag ZnO FBAR gas sensor are designed and analyzed for their performance on room temperature CO2 gas sensing, which fall into the scope of physisorption. In contrast, a Langasite (LGS) surface acoustic wave (SAW) based acetone vapor sensor is designed, developed, and tested, which is based on the chemisorption analysis of the LGS substrate. Moreover, solid state gas sensors are characterized and analyzed for chemisorption-based sensitive sensing thin film development, which can be further applied to piezoelectric-based gas sensors (i.e. Ca doped ZnO LGS SAW gas sensors) for performance enhanced CO2 gas sensing. Additionally, an innovative MEMS micro cantilever beam is proposed based on the LGS nanofabrication, which can be potentially applied for gas sensing, when combined with ZnO nanorods deposition. Principal component analysis (PCA) is employed for cross-sensitivity analysis, by which high temperature gas sensing in a real environment can be achieved. The proposed gas sensing systems are designated to work in a high temperature environment by taking advantage of the high temperature stability of the piezoelectric substrates.

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Udina, Oliva Sergi. "Smart Chemical Sensors: Concepts and Application". Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/84079.

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This PhD thesis introduces basic concepts of smart chemical sensors design, which are afterwards applied to a particular application: the analysis of natural gas. The thesis addresses thus two sets of objective, a first set of objectives related to the conceptual design of a smart chemical sensor using smart sensor standards: - The design of an optimal smart chemical sensor architecture - The novel combination in a working prototype of the highly complementary smart sensor standards IEEE-1451 and BS-7986 A second set of objectives is directly related to the selected application. Natural gas quality control. Natural gas is an energy source of major importance in the world energy supply, its quality control is increasingly important due to its origin-dependent properties and the progressive liberalization of the energy market. The objectives related to this application are: - To solve the natural gas quality analysis problem by using a lower cost approach taking advantage of MEMS technology, smart sensor features, and embedded intelligent signal processing. - To select suitable sensing technologies and associated signal processing. An overall goal addressed by the PhD Thesis is in the end the reporting of a working smart sensor prototype implementing all the smart sensor features, MEMS based natural gas analysis and advanced signal processing as a demonstration of a novel low-cost and high speed natural gas analyzer. The thesis covers this research along 7 chapters, introducing the concepts and application in chapters 1 and 2, the objectives in chapter 3, the simulation of a proposed MEMS sensor approach in chapter 4, the description of the advanced signal processing approach adopted in chapter 5, the description of the electronics and engineering of the smart natural gas analyzer prototype in chapter 6, and finally the conclusions of the work in chapter 7.
La tesis introduce conceptos básicos sobre el diseño de sensores químicos inteligentes, en particular presenta los estándares propuestos IEEE-1451 y BS-7986, y elabora una propuesta para el diseño óptimo de dichos sensores químicos inteligentes. Se implementa la propuesta de diseño para una aplicación concreta, el análisis de gas natural. Además de la aplicación de los conceptos sobre sensores químicos inteligentes se pretende además diseñar un analizador compacto, rápido y de bajo coste, para ello se estudia el uso de un microsensor termoeéctrico como sensor principal del analizador. Una vez probada su viabilidad se implementan ambos conceptos (sensores inteligentes y microsensor termoeléctrico) en un prototipo funcional validado en laboratorio. Como resultado se obtiene una propuesta para el diseño de sensores químicos inteligentes basada en estándares, y por otro lado se presenta un nuevo analizador de gas natural, más rápido y compacto que los existentes. Los resultados obtenidos originan diversas publicaciones en revistas así como dos patentes de método y sistema.

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Haapalainen, T. (Tomi). "Gas response properties of metal oxide nanoparticle based sensors on MEMS microhotplate platforms". Master's thesis, University of Oulu, 2015. http://jultika.oulu.fi/Record/nbnfioulu-201509031953.

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Abstract. This thesis concentrated on the analysis of the gas response properties of several metal oxide based gas sensors. A thin layer of chosen metal oxide was deposited on SGX Sensortech S.A. sensor platforms using pulsed laser deposition (PLD). Metal oxides used in the studies included tungsten trioxide (WO₃3), tin oxide zinc oxide (SnO₂-ZnO) and vanadium pentoxide (V₂O₅). The films were deposited at room temperature and various oxygen partial pressures, and were then post-annealed at 400 °C. Gas response measurements were done in two different temperatures and using several gases including nitrogen oxides (NOx), carbon monoxide (CO), hydrogen (H₂), and ammonia (NH₃). The concentration of the gases were varied during each measurement to probe the sensitivity of the sensors. Gas sensing performance of the sensors were evaluated based on material, selectivity toward different gases, and the effect of surface structure. Oxygen partial pressure during PLD had a clear impact on the structure of the oxide film. Higher pressure resulted in larger agglomerates of particles, which in general leads to lower gas sensitivity due to factors such as grain size and surface area-to-volume ratio. The measurements showed high responses to NOx for WO₃ and SnO₂-ZnO samples, as expected. Also, flipping of the response from low concentration to high concentration was observed for WO₃ and SnO₂-ZnO while V₂O₅ showed a mostly stable response.Metallioksidinanopartikkeleihin perustuvien kaasuantureiden analysointi MEMS-rakenteissa. Tiivistelmä. Tässä työssä analysoitiin useiden metallioksideihin perustuvien antureiden kaasuvasteita. Kaasuantureiden substraattina käytettiin SGX Sensortech S.A. valmistamia mikrolämmittimeen pohjautuvia MEMS-rakenteita. Substraatin päälle kasvatettiin ohut kerros valittuja metallioksideja, kuten volframioksidi (WO₃), tinaoksidin ja sinkkioksidin yhdiste (SnO₂-ZnO), ja vanadiumoksidi (V₂O₅). Kasvatusmenetelmänä käytettiin pulssilaserkasvatusta. Kasvatus tapahtui huoneenlämmössä ja useissa eri hapen osapaineissa. Kasvatuksen jälkeen anturit jälkihehkutettiin 400 °C lämpötilassa. Kaasuvastemittaukset suoritettiin kahdessa eri lämpötilassa usealle eri kaasulle, kuten typpioksideille (NOx), hiilimonoksidille (CO), vetykaasulle (H₂) ja ammoniakille (NH₃). Kaasun konsentraatiota vaihdeltiin mittausten aikana antureiden herkkyyden määrittämiseksi. Kaasuantureiden toimintakykyä arvioitiin materiaalin, selektiivisyyden ja oksidin pintarakenteen perusteella. Hapen osapaineella pulssilaserkasvatuksen aikana oli merkittävä vaikutus oksidikerroksen rakenteeseen. Suuremmassa paineessa kasvatetut kerrokset muodostivat suurempia partikkeleiden agglomeraatteja, mikä yleisesti ottaen johti heikompaan kaasuvasteeseen johtuen suuremmasta partikkelikoosta ja pienemmästä pinta-alan ja tilavuuden suhteesta. Mittauksissa nähtiin voimakkaita reaktioita typpioksidikaasuihin erityisesti SnO₂-ZnO ja WO₃ näytteiden osalta, kuten oli odotettavissa. SnO₂-ZnO ja WO₃ näytteillä oli myös havaittavissa kaasuvasteen suunnan muutos redusoivasta oksidoivaan kaasukonsentraation kasvaessa, kun taas V₂O₅5-näytteet käyttäytyivät enimmäkseen vakaasti.

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Puigcorbé, Punzano Jordi. "Anàlisi termo-mecànica d'estructures micromecanitzades per a sensors de gas". Doctoral thesis, Universitat de Barcelona, 2003. http://hdl.handle.net/10803/1509.

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En aquest treball s'ha establert una metodologia d'anàlisi i caracterització del comportament tèrmic, mecànic i termomecànic d'estructures micromecanitzades per a sensors de gas a través de la combinació de simulacions numèriques i tècniques de caracterització de microsistemes (mesures electro-tèrmiques, termografia, nanoindentació, AFM, XRD, microscopia confocal, Auger).
L'estudi del comportament tèrmic de les estructures micromecanitzades ha permès obtenir les característiques bàsiques que controlaran el comportament del sensor, com són el consum en potència, la distribució de temperatura i el temps de resposta del substrat. L'anàlisi termomecànic ha consistit en determinar els esforços residuals en cada estructura així com l'estudi de la deformació dels diferents dissenys per a diferents temperatures de treball. S'han identificat diferents mecanismes de degradació en els materials que formen els sensors i s'ha obtingut el comportament termomecànic fins la ruptura del sensor. Tant en l'estudi tèrmic com en el termomecànic, la interacció entre la capa sensora i el substrat micromecanitzat així com l'influencia del material sensor en el comportament global del dispositiu han estat aspectes investigats.
El treball inclou, a més, la caracterització termomecànica del Pt-Ti emprat en estructures micromecanitzades a través de la utilització de mètodes de Nanoindentació, Microscopia de Forces Atòmiques (AFM), Difracció de Raigs X (XRD) i espectroscopia Auger.
També inclou el desenvolupament d'una metodologia per predir la fatiga tèrmica en microsistemes basada en la combinació dels models elasto-plàstics de metalls en capa prima (Alumini, Pt-Ti) amb simulacions numèriques.
Finalment, de la metodologia d'anàlisi electro-termo-mecànic que s'ha dut a terme, es poden obtenir regles de disseny per la implementació de microsistemes que treballin en diferents règims de temperatura i en concret, directament aplicables al disseny i fabricació d'estructures micromecanitzades per a sensors de gas
This work presents a complete thermomechanical study of different micromachined gas sensor substrates based on closed and suspended membrane microstructures. The work has been carried out combining coupled electro-thermo-mechanical three-dimensional finite element method simulations with different experimental techniques such as those used in Microsystems characterization (thermo-electrical, thermography, AFM, XRD, confocal microscopy, Auger..). The performances predicted by simulations, such as the power consumption, the temperature distribution, the time response, the membrane deflection during operation and the preferential failure sites in the micromachined substrates have been confirmed by experience.
The work includes the thermo-mechanical characterization of Pt-Ti thin films used in the structures using Nanoindentation, AFM, XRD and Auger spectroscopy. Additionally, a methodology to predict the thermal fatigue in microsystems, which combines experimental thin metal elasto-plastic models (Al, Pt-Ti) and coupled thermo-mechanical FEM simulations, has been developed.
The good agreement between simulations and experimental results validates the numerical models, and allows us to consider the adaptability of the analyzed designs as micromachined substrates for integrated gas sensors.

Keywords: MEMS, Microsystems, gas sensors, thermal fatigue, Al, Pt-Ti, FEM.
En este trabajo se ha establecido una metodología de análisis y caracterización térmica y termomecánica de estructuras micromecanizadas en silicio para aplicaciones en sensores de gas. Esta investigación ha combinado simulaciones numéricas mediante el método de los elementos finitos con técnicas experimentales de caracterización utilizadas en el campo de los microsistemas (medidas electro-térmicas, termografía, AFM, XRD, microscopia confocal, Auger).
El estudio térmico de dichas estructuras ha permitido obtener su consumo en potencia, la distribución de temperaturas, la dinámica térmica, así como ha permitido fijar con precisión las propiedades térmicas de los materiales típicamente utilizados en la tecnología de los microsistemas. El estudio mecánico ha permitido obtener los esfuerzos residuales inducidos por los procesos de fabricación. Además, se ha obtenido la deformación de las estructuras a diferentes temperaturas de trabajo hasta la ruptura total de las membranas. Durante las altas temperaturas de trabajo se han detectado y analizado diferentes mecanismos de degradación en los materiales.
El trabajo incluye además, la caracterización termo-mecánica del Pt-Ti depositado por sputtering, ampliamente utilizado en microsensores de gas, mediante el empleo de técnicas de Nanoindentación, Microscopia AFM, Difracción de Rayos X (XRD) y espectrocopia Auger.
También presenta el desarrollo de una metodología para la predicción de la fatiga térmica en microsistemas, que se basa en la combinación de modelos elasto-plásticos para metales en capa delgada con simulaciones numéricas.
Finalmente, de la metodología de análisis termo-mecánico que se ha llevado a cabo, se pueden obtener reglas de diseño para microsistemas que trabajen a diferentes temperaturas, y en concreto directamente aplicables al diseño y fabricación de estructuras micromecanizadas para sensores de gas.

Palabras clave: MEMS, microsistemas, sensores de gas, fatiga térmica, Al, Pt-Ti, MEF.

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Nagaiah, Narasimha. "NOVEL CONCEPTUAL DESIGN AND ANLYSIS OF POLYMER DERIVED CERAMIC MEMS SENSORS FOR GAS TURBINE ENVIRONMENT". Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4086.

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Technical challenges for developing micro sensors for Ultra High Temperature and turbine applications lie in that the sensors have to survive extremely harsh working conditions that exist when converting fuel to energy. These conditions include high temperatures (500-1500°C), elevated pressures (200-400 psi), pressure oscillations, corrosive environments (oxidizing conditions, gaseous alkali, and water vapors), surface coating or fouling, and high particulate loading. Several technologies are currently underdeveloped for measuring these parameters in turbine engines. One of them is an optical-based non-contact technology. However, these nondirective measuring technologies lack the necessary accuracy, at least at present state. An alternative way to measure these parameters without disturbing the working environments is using MEMS type sensors. Currently, the techniques under development for such harsh environment applications are silicon carbide (SiC) and silicon nitrite (Si3N4) –based ceramic MEMS sensors. But those technologies present some limitation such as narrow processing method, high cost (materials and processing cost), and limited using temperatures (typically < 800 C). In this research we propose to develop two sensors based on recently developed polymer-derived ceramics (PDCs): Constant Temperature Hot wire Anemometer, temperature/heat-flux sensor for turbine applications. PDC is a new class of high temperature ceramics. As we shall describe below, many unique features of PDCs make them particularly suitable for the proposed sensors, including: excellent thermo-mechanical properties at high temperatures, enable high temperature operation of the devices; various well-developed processing technologies, such as injection molding,photolithography, embossing, DRIE etching and precise machining, can be used for the fabrication of the devices; and tunable electric conductivity, enable the proposed sensors fabricated from similar materials, thus reliability considerations associated with thermal mismatch, which is a big concern when using MEMS-based sensors at elevated temperatures, will be minimized.
M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering

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Gong, Jianwei. "NON-SILICON MICROFABRICATED NANOSTRUCTURED CHEMICAL SENSORS FOR ELECTRIC NOSE APPLICATION". Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4082.

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A systematic investigation has been performed for "Electric Nose", a system that can identify gas samples and detect their concentrations by combining sensor array and data processing technologies. Non-silicon based microfabricatition has been developed for micro-electro-mechanical-system (MEMS) based gas sensors. Novel sensors have been designed, fabricated and tested. Nanocrystalline semiconductor metal oxide (SMO) materials include SnO2, WO3 and In2O3 have been studied for gas sensing applications. Different doping material such as copper, silver, platinum and indium are studied in order to achieve better selectivity for different targeting toxic gases including hydrogen, carbon monoxide, hydrogen sulfide etc. Fundamental issues like sensitivity, selectivity, stability, temperature influence, humidity influence, thermal characterization, drifting problem etc. of SMO gas sensors have been intensively investigated. A novel approach to improve temperature stability of SMO (including tin oxide) gas sensors by applying a temperature feedback control circuit has been developed. The feedback temperature controller that is compatible with MEMS sensor fabrication has been invented and applied to gas sensor array system. Significant improvement of stability has been achieved compared to SMO gas sensors without temperature compensation under the same ambient conditions. Single walled carbon nanotube (SWNT) has been studied to improve SnO2 gas sensing property in terms of sensitivity, response time and recovery time. Three times of better sensitivity has been achieved experimentally. The feasibility of using TSK Fuzzy neural network algorithm for Electric Nose has been exploited during the research. A training process of using TSK Fuzzy neural network with input/output pairs from individual gas sensor cell has been developed. This will make electric nose smart enough to measure gas concentrations in a gas mixture. The model has been proven valid by gas experimental results conducted.
Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering

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CICIOTTI, FULVIO. "Oscillator-Based CMOS Readout Interfaces for Gas Sensing Applications". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241089.

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Il rilevamento di gas tossici e pericolosi è sempre stato necessario per motivi di sicurezza. Negli ultimi anni, in particolare, l’attenzione per lo sviluppo di sistemi portatili e a basso costo per il rilevamento dei gas è aumentata notevolmente. Questa tesi presenta circuiti CMOS versatili, veloci, ad alta precisione e basso consumo per applicazioni portatili di rilevamento di gas. I sensori target sono i Metal Oxide Semiconductor (MOX). Questi sensori sono ampiamente utilizzati per la loro intrinseca compatibilità con le tecnologie MEMS integrate. Le tipologie di lettura scelte sono basate su un oscillatore controllato dalla resistenza del sensore stessa, in modo da ottenere una conversione resistenza-tempo. Ciò garantisce un ampio range dinamico, una buona precisione e la capacità di far fronte alle grandi variazioni di resistenza del sensore MOX. Quattro diversi prototipi sono stati sviluppati e testati con successo. Sono state anche eseguite misurazioni chimiche con un vero sensore SnO2 MOX, validando i risultati ottenuti. Le misure hanno mostrato come il sensore e l’interfaccia sia in grado di rilevare fino a 5ppm di CO in aria. Gli ASIC sono in grado di coprire 128 dB di DR a 4Hz di output data rate digitale, o 148 dB a 0.4Hz, garantendo un errore relativo percentuale sempre migliore dello 0,4% (SNDR> 48 dB). Le prestazioni target sono state raggiunte con aggressive strategie di progettazione e ottimizzazione a livello di sistema. È stata utilizzata una tecnologia CMOS a 130nm fornita da Infineon Technologies AG. La scelta di un nodo tecnologico così scalato (rispetto alle tipiche implementazioni in questo settore) ha consentito di ridurre ulteriormente i consumi fino a circa 450 μA. Inoltre, questo lavoro introduce la possibilità di utilizzare la stessa architettura basata su oscillatore per eseguire la lettura di sensori capacitivi. I risultati delle misurazioni con sensori capacitivi MEMS hanno mostrato 116 dB di DR, con un SNR di 74 dB a 10Hz di velocità di trasmissione dati digitale. Le architetture sviluppate in questa tesi sono compatibili con gli standard moderni nel settore del rilevamento del gas per dispositivi portatili.
Detection of toxic and dangerous gases has always been a need for safety purpose and, in recent years, portable and low-cost gas sensing systems are becoming of main interest. This thesis presents fast, high precision, low-power, versatile CMOS interface circuits for portable gas sensing applications. The target sensors are Metal Oxide Semiconductor (MOX) sensors which are widely used due to their inherent compatibility with integrated MEMS technologies. The chosen readout typologies are based on the time-domain Resistor-Controlled Oscillator. This guarantees wide dynamic range, good precision and the ability to cope with the large MOX sensor resistance variations. Four different prototypes have been successfully developed and tested. Chemical measurements with a real SnO2 MOX sensor have also been performed to validate the results, showing a minimum CO detection capability in ambient air of 5 ppm. The ASICs are able to cover 128 dB of DR at 4 Hz of digital output data rate, or 148 dB at 0.4 Hz, while providing a relative error always better than 0.4% (SNDR >48 dB). Target performances have been achieved with aggressive design strategies and system-level optimization, and using a scaled (compared to typical implementations in this field) 130nm CMOS technology provided by Infineon Technologies AG. Power consumption is about 450 μA. Moreover, this work introduces the possibility to use the same oscillator-based architecture to perform capacitive sensors readout. Measurement results with capacitive MEMS sensors have shown 116 dB of DR in CSENS mode, with an SNR of 74 dB at 10 Hz of digital output data rate. The architectures developed in this thesis are compatible with the modern standards in the portable gas sensing industry.

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Navaei, Milad. "Integration of a micro-gas chromatography system for detection of volatile organic compounds". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53924.

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The focus of this dissertation is on the design and micro-fabrication of an all silicon gas chromatography column with a novel two dimensional resistive heater and on its integration with an ultra-low power Thermal Conductivity Detector (TCD) for fast separation and detection of Volatile Organic Compounds (VOC). The major limitations of the current MEMS-GC column are: direct bonding of silicon to silicon, and peak band broadening due to slow temperature programming. As part of this thesis, a new gold eutectic-fusion bonding technique is developed to improve the sealing of the column. Separation of BETX, alkane mixture and VOCs were demonstrated with the MEMS GC column. The time and power required to ramp and sustain the column’s temperature are very high for the current GC columns. To reduce the time required to separate the compounds, a new temperature gradient programming heating method was developed to generate temperature gradients along the length of the column. This novel heating method refocuses eluding bands and counteracts some of the chromatographic band spreading due to diffusion resulting in an improved separation performance. A low power TCD was packaged and tested in a GC by comparison against FID for the detection of a mixture of VOCs. It demonstrated low power operation of a few milliwatts and a very fast response. The MEMS-GC was also demonstrated for rapid detection of the VOC gases released by pathogenic species of Armillaria fungus.

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Sarfraz, Sohab. "A high temperature gas flow invariant thermal conductivity sensor developed in SOI CMOS MEMS technology". Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708412.

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Boudjiet, Mohand-Tayeb. "Microsystèmes durables de mesures de concentration d'hydrogène utilisant des micropoutres sans couche sensible". Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0137/document.

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Ces travaux de thèse tentent de répondre à un besoin de surveillance fiable et durable de la concentration d’hydrogène dans un environnement radioactif. Dans ces travaux, nous proposons l’étude et le développement d’un capteur physique d’hydrogène à base de micropoutres résonantes en silicium. La particularité de ce type de capteur vient du fait qu’il ne contient pas de couche sensible et est donc moins sujet au vieillissement que les capteurs chimiques à base de couche sensibles. Compte tenu de la faible masse volumique de l’hydrogène par rapport à celle de l’air et de la bonne sensibilité des micropoutres résonantes aux propriétés physiques du gaz environnant (masse volumique et viscosité), l’utilisation de micropoutres résonantes pour le suivi de la concentration de l’hydrogène dans l’air est tout à fait possible. L’objectif de ces travaux de recherche est l’amélioration de la sensibilité et de la limite de détection de ce type de capteur. Tout d’abord, une étude des méthodes de suivi de faibles variations de la fréquence de résonance a été effectuée. Ceci a permis de déterminer la méthode ayant le meilleur rapport signal sur bruit, permettant ainsi d’améliorer la limite de détection en termes de variation de fréquence de résonance. Dans une seconde partie, une étude de l’influence de la géométrie et des dimensions sur la sensibilité vis-à-vis des variations de la masse volumique du gaz environnant a été réalisée. A l’issu de cette étude, des critères géométriques et dimensionnels permettant l’optimisation de la sensibilité ont été dégagés. D’autres aspects visant à améliorer les performances (sensibilité et limite de détection) de ces capteurs ont été étudiés, comme l’influence du courant d’actionnement et des tensions de polarisation (actionnement électromagnétique et détection piézorésistive) et l’utilisation des modes supérieurs de résonance. Par ailleurs, l’étude de l’influence des paramètres environnementaux (température et pression) sur le comportement des micropoutres résonantes a été établie
These PhD research tries to meet a need for a reliable and a sustainable hydrogen concentration monitoring in a radioactive environment. In this work, we propose the study and development of resonant silicon microcantilever-based physical hydrogen sensors. The special feature of this sensor is that it does not contain any sensitive and consequently the reliability is improved, compared to devices with sensitive coating. In view of the low density of hydrogen compared to that of air, and the good sensitivity of a resonant microcantilever to the physical properties of the surrounding gas (density and viscosity), the use of vibrating uncoated microcantilever for monitoring hydrogen concentration in air is therefore possible. The objective of this research is to improve the sensitivity and the limit of detection of such sensors. First of all, a study of methods for monitoring small changes in resonant frequency has been conducted in order to determine the method having the best signal to noise ratio, thus, allowing improvement of its resolution in terms of resonant frequency variation measurement. In a second part, a study of the influence of microcantilever geometries and dimensions on their sensitivity to the gas density variation has been performed. As a result, geometrical and dimensional criteria for optimizing the sensitivity to the gas density have been identified. Other factors in a view of improving performance (sensitivity and detection limit) of vibrating microbeams have been studied, such as the influence of the actuating current and bias voltages (electromagnetic actuation and piezoresistive detection) and using high resonant modes. Furthermore, the study of the influence of environmental parameters (temperature and pressure) on the sensors behavior has been established

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TOMMASI, ALESSIO. "Integration of ZnO nanostructures onto a microhotplate for gas sensing". Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2641068.

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Abstract Due to their special shapes, compositions, chemical and physical properties, one dimensional (1D) or quasi 1D metal oxide nanostructures are widely employed in gas sensor devices and many others. Tetrapods (TPs) nanostructures are one of the many different ZnO shapes, that could be exploited for high-performance chemical sensors. TPs structures can be obtained by vapor phase growth, which is a simple and cost-effective approach for growing micro and nanoparticles on a relatively large scale. Microsystems technology intrinsically offers a powerful tool to obtain low cost, high efficiency and long-term devices. In Microsystems technology, micromachined hotplates are mainly used for sensor applications where the active sensing material is deposited onto the membrane integrated with electrical stimuli and readout. The microhotplate presents a series of advantages such as miniaturized size, fast response, high sensitivity, low power consumption and implementable selectivity. In this view, a nanostructured layer on a thin membrane allows for increasing the sensing performance and obtaining a highly sensitive sensor, while decreasing power consumption. The current efforts to integrate nanostructures on a microdevices, lack to find out a cost-efficient method. In this thesis the process for the fabrication of a Micro Electro-Mechanical System (MEMS) based gas sensor that integrates a ZnO TPs layer is successfully developed. In particular, the integration of the nanostructures is achieved using a cost-effective patterning method. TPs are dispersed in a 2-propanol (IPA) suspension and precipitated onto the membrane. The nanostructures form a sensitive layer patterned through a polydimethylsiloxane (PDMS) physical mask with a central window. The deposition of TPs is performed by centrifugation in order to obtain a homogeneous dispersion and a as thin as possible packed layer on the membrane. The final device is a square shaped die, with a suspended Si3N4 membrane in the centre. The interdigitated Au/Ti electrodes and a Pt/Ta resistor are fabricated on the suspended Si3N4 membrane. In particular, the Pt/Ta resistor is embedded in a dielectric layer in order to optimize the temperature distribution and is used both for heating the microhotplate and getting temperature readout. A highly porous film of entangled ZnO TPs is deposited between the interdigitated electrodes ensuring the electrical contact. Such a device is able to respond as a variable resistance as a function of gas target concentration at determinate temperatures. The device is tested by varying the concentration of target gases in the atmosphere of a test chamber. The sensor response proves the device functionality and, with the top-down integration approach, enables Very Large Scale Integration (VLSI) production.

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Watanabe, Naoki. "Fundamental Study on Wide-Bandgap-Semiconductor MEMS and Photodetectors for Integrated Smart Sensors". 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174944.

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Mahdavifar, Alireza. "Computational and experimental development of ultra-low power and sensitive micro-electro-thermal gas sensor". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54923.

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In this research a state-of-the-art micro-thermal conductivity detector is developed based on MEMS technology. Its efficient design include a miniaturized 100×2 µm bridge from doped polysilicon, suspended 10 µm away from the single crystalline silicon substrate through a thermally grown silicon dioxide sacrificial layer. The microbridge is covered by 200 nm silicon nitride layer to provide more life time. Analytical models were developed that describe the relationship between the sensor response and ambient gas material properties. To obtain local temperature distribution and accurate predictions of the sensor response, a computational three dimensional simulation based on real geometry and minimal simplifications was prepared. It was able to handle steady-state and transient state, include multiple physics such as flow, heat transfer, electrical current and thermal stresses. Two new methods of measurement for micro TCD were developed; a time resolved method based on transient response of the detector to a step current pulse was introduced that correlates time constant of the response to the concentration of gas mixture. The other method is based on AC excitation of the micro detector; the amplitude and phase of the third harmonic of the resulting output signal is related to gas composition. Finally, the developed micro-sensor was packaged and tested in a GC system and was compared against conventional and complex FID for the detection of a mixture of VOCs. Moreover compact electronics and telemetry modules were developed that allow for highly portable applications including microGC utilization in the field.

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Kankanam, Gamage Sisira. "Exploration of Novel Silicon Devices Toward the Realization of a MEMS-Based Microsystem for Utilities (Water, Gas, Electrical) Monitoring". University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin985901586.

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Lefebvre, Anthony. "Simulation et conception de microsources infrarouges nanophotoniques pour la détection de gaz". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLO002/document.

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L’utilisation de micromembranes suspendues chauffées par effet Joule comme source de rayonnement infrarouge est une piste prometteuse pour la réalisation de détecteurs de gaz compacts, basse consommation et à bas coût. Afin d’améliorer l’efficacité de ces dispositifs récemment introduits, il est nécessaire d’optimiser ceux-ci à la fois du point de vue optique et thermique.En ajoutant des résonateurs plasmoniques frustrés sur les membranes, il est possible de modifier l’émissivité de ces dernières, afin de contrôler spectralement et angulairement le rayonnement émis. De cette façon, la puissance utile est augmentée, tandis que la consommation électrique diminue. D’autre part, l’étude en profondeur des rôles des différents canaux thermiques conduit à relier rayon de la membrane, temps de chauffe et énergie disponible par mesure et de définir un régime optimal de fonctionnement dynamique.Finalement les membranes sont fabriquées en salle blanche et caractérisées électriquement, optiquement et mécaniquement afin d’estimer les gains en performances. La réalisation d’un prototype de capteur de CO2 à 4,26 µm à partir de ces sources indique des précisions de l’ordre de la vingtaine de ppm pour une consommation d’un milliwatt, en compétition favorable avec l’état de l’art mondial dans ce domaine
Joule-heated suspended microhotplates can be used as infrared sources in cheap, low-consumption spectroscopic gas sensors. To enhance the very low efficiency of first generation structures, both their thermal and optical designs have to be optimized.The implementation of frustrated plasmonic resonators on top of the membrane grants both spectral and angular control of its emissivity. It is thus possible to make it radiate only at the frequencies absorbed by the gas under study, and in the solid angle of the detector. This leads to an increase in useful radiated power while the overall electrical consumption is decreased. Dynamical studies of membrane heating provide welcome insight on the relationship between membrane radius, heating time and energy consumption per measurement. The existence of a compromise is demonstrated in order to maximize the radiative efficiency, and its physical interpretation is detailed.Eventually, membranes fabricated in LETI’s clean room were characterized to measure their electrical, optical and mechanical properties. The implementation of such sources in a CO2 prototype sensor led to state-of-the-art results, with a few dozen ppm sensitivity with a power consumption of only one milliwatt

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Antelius, Mikael. "Wafer-scale Vacuum and Liquid Packaging Concepts for an Optical Thin-film Gas Sensor". Doctoral thesis, KTH, Mikro- och nanosystemteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119839.

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This thesis treats the development of packaging and integration methods for the cost-efficient encapsulation and packaging of microelectromechanical (MEMS) devices. The packaging of MEMS devices is often more costly than the device itself, partly because the packaging can be crucial for the performance of the device. For devices which contain liquids or needs to be enclosed in a vacuum, the packaging can account for up to 80% of the total cost of the device. The first part of this thesis presents the integration scheme for an optical dye thin film NO2-gas sensor, designed using cost-efficient implementations of wafer-scale methods. This work includes design and fabrication of photonic subcomponents in addition to the main effort of integration and packaging of the dye-film. A specific proof of concept target was for NO2 monitoring in a car tunnel. The second part of this thesis deals with the wafer-scale packaging methods developed for the sensing device. The developed packaging method, based on low-temperature plastic deformation of gold sealing structures, is further demonstrated as a generic method for other hermetic liquid and vacuum packaging applications. In the developed packaging methods, the mechanically squeezed gold sealing material is both electroplated microstruc- tures and wire bonded stud bumps. The electroplated rings act like a more hermetic version of rubber sealing rings while compressed in conjunction with a cavity forming wafer bonding process. The stud bump sealing processes is on the other hand applied on completed cavities with narrow access ports, to seal either a vacuum or liquid inside the cavities at room temperature. Additionally, the resulting hermeticity of primarily the vacuum sealing methods is thoroughly investigated. Two of the sealing methods presented require permanent mechanical fixation in order to complete the packaging process. Two solutions to this problem are presented in this thesis. First, a more traditional wafer bonding method using tin-soldering is demonstrated. Second, a novel full-wafer epoxy underfill-process using a microfluidic distribution network is demonstrated using a room temperature process.

QC 20130325

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Truax, Stuart. "A microscale chemical sensor platform for environmental monitoring". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45780.

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The objective of this research is to apply micromachined silicon-based resonant gravimetric sensors to the detection of gas-phase volatile organic compounds (VOCs). This is done in two primary tasks: 1) the optimization and application of silicon disk resonators to the detection of gas-phase VOCs, and 2) the development and application of a novel gravimetric-capacitive multisensor platform for the detection of gas-phase VOCs. In the rst task, the design and fabrication of a silicon-based disk resonator structure utilizing an in-plane resonance mode is undertaken. The resonance characteristics of the disk resonator are characterized and optimized. The optimized characteristics include the resonator Q-factor as a function of geometric parameters, and the dynamic displacement of the in-plane resonance mode. The Q-factors of the disk resonators range from 2600 to 4360 at atmosphere for disk silicon thicknesses from 7 µm to 18 µm, respectively. The resonance frequency of the in-plane resonance mode ranges from 260 kHz up to 750 kHz. The disk resonators are applied to the sensing of gas-phase VOCs using (poly)isobutylene as a sensitive layer. Limits of detection for benzene, toluene and m-xylene vapors of 5.3 ppm, 1.2 ppm, and 0.6 ppm are respectively obtained. Finally, models for the limits of detection and chemical sensitivity of the resonator structures are developed for the case of the polymer layers used. In the second task, a silicon-based resonator is combined with a capacitive structure to produce a multisensor structure for the sensing of gas-phase VOCs. Fabrication of the multisensor structure is undertaken, and the sensor is theoretically modeled. The baseline capacitance of the capacitor component of the multisensor is estimated to be 170 fF. Finally, initial VOC detection results for the capacitive aspect of the sensor are obtained.

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Mohammadi, Saeed. "Phononic band gap micro/nano-mechanical structures for wireless communications and sensing applications". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/41069.

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Because of their outstanding characteristics, micro/nano-mechanical (MM) structures have found a plethora of applications in wireless communications and sensing. Many of these MM structures utilize mechanical vibrations (or phonons) at megahertz or gigahertz frequencies for their operation. On the other hand, the periodic atomic structure of crystals is the fundamental phenomenon behind the new era of electronics technology. Such atomic arrangements lead to a periodic electric potential that modifies the propagation of electrons in the crystals. In some crystals, e.g. silicon (Si), this modification leads to an electronic band gap (EBG), which is a range of energies electrons can not propagate with. Discovering EBGs has made a revolution in the electronics and through that, other fields of technology and the society. Inspired by these trends of science and technology, I have designed and developed integrated MM periodic structures that support large phononic band gaps (PnBGs), which are ranges of frequencies that phonons (and elastic waves) are not allowed to propagate. Although PnBGs may be found in natural crystals due to their periodic atomic structures, such PnBGs occur at extra high frequencies (i.e., terahertz range) and cannot be easily engineered with the current state of technology. Contrarily, the structures I have developed in this research are made on planar substrates using lithography and plasma etching, and can be deliberately engineered for the required applications. Although the results and concepts developed in this research can be applied to other substrates, I have chosen silicon (Si) as the substrate of choice for implementing the PnBG structure due to its unique properties. I have also designed and implemented the fundamental building blocks of MM systems (e.g., resonators and waveguides) based on the developed PnBG structures and have shown that low loss and efficient MM devices can be made using the PnBG structures. As an example of the possible applications of these PnBG structures, I have shown that an important source of loss, the support loss, can be suppressed in MM resonators using PnBG structures. I have also made improvements in the characteristics of the developed MM PnBG resonators by developing and employing PnBG waveguides. I have further shown theoretically, that photonic band gaps (PtBGs) can also be simultaneously obtained in the developed PnBGs structures. This can lead to improved photon-phonon interactions due to the effective confinement of optical and mechanical vibrations in such structures. For the design, fabrication, and characterization of the structures, I have developed and utilized complex and efficient simulation tools, including a finite difference time domain (FDTD), a plane wave expansion (PWE), and a finite elements (FE) tool, each of which I have developed either completely from scratch, or by modification of an existing tool to suit my applications. I have also developed and used advanced micro-fabrication recipes, and characterization methods for realizing and characterizing these PnBG structures and devices. It is agued that by using the same ideas these structures can be fabricated at nanometer scales to operate at ultra high frequency ranges. I believe my contributions has opened a broad venue for new MM structures based on PnBG structures with superior characteristics compared to the conventional devices.

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Gaddis, Christopher Stephen. "Diatom Alchemy". Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7611.

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This work resulted in the development of multiple distinct and novel methods of cheaply producing large numbers of biologically derived, complex, 3-dimensional microstructures in a multitude of possible compositions. The biologically derived structures employed in this work were diatoms, a type of single celled algae, which grow complex silica shells in species-specific shapes. Due to the wide diversity of naturally occurring diatom shapes (on the order of 105), and the flexibility in tailoring chemical compositions using the methods developed here, real potential exists for cheaply mass-producing industrially relevant quantities of controlled shape and size 3-d particles for the first time. The central theme of this research is the use of diatoms as a transient scaffold onto which a coating is applied. After curing the coating, and in some cases firing the coating to form ceramic, the diatom can be selectively etched away leaving a free standing replica of the original structure with the salient features of the pre-form intact, but now composed of a completely different material. Using this concept, specific methods were developed to suit various precursors. Dip coating techniques were used to create epoxy diatoms, and silicon carbide diatoms. The Sol-Gel method was used to synthesize zirconia diatoms in both the tetragonal and monoclinic phases. A multi step method was developed in which previously synthesized epoxy diatoms were used as a template for deposition of a silicon carbide precursor and then heat treated to produce a silicon carbide/carbon multi-component ceramic. A hydrothermal reaction was also developed to convert Titania diatoms to barium titanate by reaction with barium hydroxide. Finally, the device potential of diatom-derived structures was conclusively demonstrated by constructing a gas sensor from a single Titania diatom. Under suitable conditions, the sensor was found to have the fastest response and recovery time of any sensor of this type reported in the literature. Furthermore, this work has laid the groundwork for the synthesis of many other tailored compositions of diatoms, and provided several compositions for device creation.

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Tortissier, Grégory. "Étude et développement d’une plateforme de détection chimique à ondes acoustiques de surface pour environnement sévère haute température". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13859/document.

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Ces travaux ont donc visé le développement d’une plateforme complète de détection de gaz pour environnement sévère haute température. Cette plateforme intègre un dispositif à ondes acoustiques de surface sur substrat Langasite, une résistance chauffante, une couche sensible inorganique nanostructurée et est placée dans une enceinte hermétique. Des températures de l’ordre de 450°C ont été atteintes et des tests de cyclages ont démontré un fonctionnement en accord avec les modèles théoriques et une reproductibilité des mesures. Des tests de détection de composés organiques volatils (éthanol et toluène) ont mis en avant des seuils de détection de l'ordre de quelques ppm
Measuring pollutants concentrations in gas and vapors emissions are important environmental issues. This work presents a stand-alone portable device for high temperature assessment. The system includes a Langasite (LGS) acoustic sensor, a ceramic heater and a platform with RF connections for remote in-situ measurements. The packaging consists in a hermetic stainless steel cell which enables safe gas detection. In situ temperature measurements have been achieved and the thermal behavior was successfully investigated in the temperature range 25-450°C. The designed cell highlights good agreement with theoretical models and reproducibility of the measures. Volatile organic compounds exposures have been investigated and promising ppm level detections have been obtained

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Xiang, Shu. "Piezoelectric thin films and nanowires: synthesis and characterization". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41139.

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Piezoelectric materials are widely used for sensors, actuators and trasducers. Traditionally, piezoelectric applications are dominated by multicomponent oxide ferroelectrics such as lead zirconate titanate (PZT), which have the advantage of high piezoelectric coefficients. Recently, one-dimensional piezoelectric nanostructures such as nanowires of zinc oxide (ZnO) and gallium nitride (GaN) has gained a lot of attention due to their combined piezoelectric and semiconducting properties. The focus of this thesis is to study the processing and electric properties of such piezoelectric thin films and nanostructures for various applications. There is an increasing interest to form thin films of multicomponent ferroelectric oxides such as PZT on three-dimensional structures for charge storage and MEMS applications. Traditional vapor phase deposition techniques of PZT offer poor conformality over threedimensional surfaces due to their reactant transport mechanisms. As an alternative, solgel synthesis may provide new process possibilities to overcome this hurdle but the film quality is usually inferior, and the yield data was usually reported for small device areas. The first part of this study is dedicated to the characterization of the electric properties and yield of PZT thin film derived from the sol-gel process. PZT thin films with good electric property and high yield over a large area have been fabricated. La doping was found to double the breakdown field due to donor doping effect. LaNiO3 thin films that can be coated on a three-dimensional surface have been synthesized by an all-nitrate based sol-gel route, and the feasibility to form a conformal coating over a three-dimensional surface by solution coating techniques has been demonstrated. ZnO and GaN micro/nanowires are promising piezoelectric materials for energy harvesting and piezotronic device applications. The second part of this study is focused on the growth of ZnO and GaN micro/nanowires by physical vapor deposition techniques. The morphology and chemical compositions are revealed by electron microscopy. Utilizing the as-grown ZnO nanowires, single nanowire based photocell has been fabricated, and its performance was studied in terms of its response time, repeatability, excitation position and polarization dependence upon He-Cd UV-laser illumination. The excitation position dependence was attributed to the competition of two opposite photo- and thermoelectric currents originated from the two junctions. The excitation polarization dependence was attributed to the difference in optical properties due to crystallographic anisotropy. Employing the as-grown GaN nanowires, single nanowire based strain sensor is demonstrated, and its behavior is discussed in terms of the effect of strain-induced piezopotential on the Schottky barrier height.

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Graf, Alexander. "Entwicklung eines miniaturisierten Ionenfilters und Detektors für die potentielle Anwendung in Ionenmobilitätsspektrometern". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-163935.

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Die Ionenmobilitätsspektrometrie ermöglicht eine selektive Detektion von niedrigkonzentrierten Gasen in Luft. Darauf beruhende Analysegeräte können verhältnismäßig einfach umgesetzt werden und in vielfältigen mobilen Einsatzszenarien wie der Umweltanalytik Anwendung finden. Die vorliegende Dissertation gibt einen Überblick über die Grundlagen der Ionenmobilitätsspektrometrie und setzt die funktionellen Teilkomponenten Ionenfilter und Ionendetektor mit Mikrosystemtechniken um. Dafür werden Möglichkeiten aus dem Stand der Technik vorgestellt und eine für die Umsetzung optimale Variante identifiziert. Ein Ionenfilter basierend auf der Differenzionenmobilitätsspektrometrie zeigt diesbezüglich ein sehr geeignetes Skalierungsverhalten. Zur Integration in einen Demonstrator-Chip wird ein neuartiges Bauelementkonzept verfolgt, mit technologischen Vorversuchen untersetzt und erfolgreich in einen Gesamtherstellungsablauf überführt. Mit Hilfe von weiterführenden analytischen Untersuchungen werden spezifische Phänomene bei der elektrischen Kontaktierung der verwendeten BSOI-Wafer als Ausgangsmaterial hergeleitet und Empfehlungen zur Vermeidung gegeben. Der Funktionsnachweis der Teilkomponente Ionendetektor wird anhand von hergestellten Demonstrator-Chips und mit Hilfe eines entwickelten Versuchsaufbaus begonnen. Es werden die weiteren Schritte zum Nachweis der Gesamtfunktionalität abgeleitet und festgehalten. Auf Basis des umgesetzten Bauelement- und Technologiekonzepts und der vorliegenden Ergebnisse, wird das entwickelte und realisierte Gesamtkonzept als sehr aussichtsreich hinsichtlich der favorisierten Verwendung als Teilkomponente eines miniaturisierten Ionenmobilitätsspektrometers eingeschätzt.

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Chou, Ping-Huan, i 鄒秉寰. "MEMS Gas Sensors Using Carbon Nanotubes With Full CMOS Compatibility". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/4a72gn.

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碩士
國立臺北科技大學
製造科技研究所
95
A class of multi-walled carbon nanotube (MWNT) gas sensors in consideration of CMOS and MEMS compatibility were proposed and developed. The sensor fabricated by CMOS-MEMS micromachining process was implemented on silicon substrate featuring a dielectric membrane and micro-heaters, and operated as a chemoresistive device. MWNTs were employed as active sensing clusters and deposited onto the membrane. MWNTs aligned laterally and linked with adjacent ones across electrodes through a room-temperature dielectrophoresis (DEP) process. Experiments to specify the sensor structure and verify sensing characteristics of MWNTs were carried out, and successfully demonstrate the reversible physisorption in response to the presence of nitrogen(H2) and sensing behaviour in response to the presence of oxygen (O2) between 2500 ppm and 7500 ppm, and carbon monoxide (CO2) between 120 ppm and 300 ppm. The more the gas concentration, the more the sensitivity. Based on this research results, it should be a fundamental and effective integration experience to combine MWCNT gas sensing applications with realization of CMOS smart gas sensor technologies in the near future.

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LIN, CHIA-MIN, i 林佳潣. "Study on Fabrication of MEMS Cantilevers for Photoacoustic Spectroscopy Gas Sensors". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/3c579a.

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碩士
國立暨南國際大學
電機工程學系
105
In this study, micro-electromechanical system (MEMS) cantilevers for the photoacoustic spectroscopy (PAS) gas sensing applications were designed and fabricated. The cantilevers were fabricated on a silicon-on-insulator (SOI) wafer with the buried oxide layer (BOX) as the sacrificial layer. The deep-reactive-ion etching (DRIE, ICP) was used to define the shape of cantilever, and for the through wafer etching. The structure was then released, removing the BOX layer, in hydrofluoric acid solution. The cantilevers were measured under a white light interferometer to determine the static out-of-plane displacement. In order to analyze the physical properties (resonance frequency, Young’s modulus, spring constant, displacement amplitudes) of cantilevers, the measurement was then taken using a laser Doppler vibrometer. This device can achieve better analytical sensitivity, highly linear response, and greater physical movement than that the conventional membrane microphone does.

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Sun, Liwei. "Design and fabrication of surface textured MEMS for infrared gas sensors". Thesis, 2004. http://spectrum.library.concordia.ca/8394/1/MR04402.pdf.

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This thesis concentrates primarily on optimum design and fabrication of novel MEMS (micro-electro-mechanical systems) infrared gas sensors. It deals with the thermal, electrical, optical and mechanical response for a spectroscopic gas sensor based on MEMS surface textured technologies. An overview of the theories of conventional and novel MEMS infrared gas sensors is presented. Two important surface modification technologies: Photonic Crystal (PC) and Surface Plasmon (SP) for the proposed devices as well as the SP dispersion relation are discussed. The structures, materials, geometries, and electrical properties of the devices for the generation of single and narrow band mid-infrared light source with high transmission efficiency are studied. Plane Wave Methods (PWM) are used to simulate Photonic Bandgap (PBG) and Finite Difference Time Domain (FDTD) methods are used to simulate the function of the proposed devices. Silicon on isolator (SOI) technology is used to design and fabricate the proposed device onto a microbridge that enable the power efficiency heating the device and enhance its sensitivity to gas concentration. This fabrication process (MicraGEM) provided by CMC (Canadian Microelectronics Corporation) and Micralyne Incorporation. Unfortunately, the devices could not be successfully fabricated although our design did not break any design rule. The main reason is that the process provided error minimum size of self-alignment etching holes. However, this design help CMC and Micralyne to identify and redefine the design rules, also push Micralyne to improve the process in the future.

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Jaber, Nizar. "Dynamic Approaches to Improve Sensitivity and Performance of Resonant MEMS Sensors". Diss., 2018. http://hdl.handle.net/10754/630094.

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The objective of this dissertation is to investigate several dynamical approaches aiming to improve the sensitivity and performance of microelectromechanical systems (MEMS) resonant sensors. Resonant sensors rely on tracking shifts in the dynamic features of microstructures during sensing, such as their resonance frequency. We aim here to demonstrate analytically and experimentally several new concepts aiming to sharpen their response, enhance the signal to noise ratio, and demonstrate smart functionalities combined into a single resonator. The dissertation starts with enhancing the excitations of the higher order modes of vibrations of clamped-clamped microbeam resonators. The concept is based on using partial electrodes with shapes that induce strong excitation of the mode of interest. Using a half electrode, the second mode is excited with a high amplitude of vibration. Also, using a two-third electrode configuration is shown to amplify the third mode resonance amplitude compared with the full electrode under the same electrical loading conditions. Then, we demonstrate the effectiveness of higher order mode excitation and metal organic frameworks (MOFs) functionalization for improving the sensitivity and selectivity of resonant gas sensors. Also, using a single mode only, we show the possibility of realizing a smart switch triggered upon exceeding a threshold mass when operating the resonator near the dynamic pull-in instability. The second part of the dissertation deals with the dynamics of the microbeam under a two-source harmonic excitation. We experimentally demonstrate resonances of an additive and subtractive type. It is shown that by properly tuning the frequency and amplitude of the excitation force, the frequency bandwidth of the resonator is controlled. Finally, we employ the multimode excitation of a single resonator to demonstrate smart functionalities. By monitoring the frequency shifts of two modes, we experimentally demonstrate the effectiveness of this technique to measure the environmental temperature and gas concentration. Also, we present a hybrid sensor and switch device, which is capable of accurately measuring gas concentration and perform switching when the concentration exceeds a specific (safe) threshold. In contrast to the single mode operation, we show that monitoring the third mode enhances sensitivity, improves accuracy, and lowers the sensor sensitivity to noise.

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Dwivedi, Priyanka. "Development of gas sensor prototypes based on semiconductor nanostructures and their integration with mems". Thesis, 2018. http://eprint.iitd.ac.in:80//handle/2074/7956.

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Liao, Kuan-Hsun, i 廖冠勛. "Novel MEMS gas sensors using mesoporous carbon nano-powderimmobilized by the dielectrophoresis process". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/rr632g.

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碩士
國立臺北科技大學
製造科技研究所
96
Innovative micro gas sensors using mesoporous carbon powder (MCP) as the sensitive film is presented for the first time with MEMS manufacturing technology. Powdered mesoporous carbon is employed as active sensing layers and deposited between electrodes on a thin membrane. The basic concept of the mesoporous carbon gas sensor features is a thin membrane (including silicon dioxide and silicon nitride) and electrodes. Mesoporous carbon layers are aligned and immobilized between electrodes over the membrane by AC-powered dielectrophoresis, Due to its nano-scale structure, the MCP active layer is found very sensitive to heater operation and thus it causes significant noise during measurement. A new method using high-voltage to recover MCP material and measure resistance changes after gas tests without heater implementation is successfully proposed. Mesoporous carbon gas sensors are tested with a variety of gases like O2, NH3 and CO and significant resistance changes are measured to detect various. The sensors are located in a vacuum environment (10-2 ~10-3 Torr) and employed gas concentrations of O2, NH3 and CO gases ranging between 500~4000ppm, 200~800ppm and 100~400ppm, respectively. The result of resistance changes at the MCP active layer is found distinct and their sensitivity is also prominent up to 14.2%. The chemoresistive effect of gas detections using MCP gas sensors is proven and promising for further applications with CMOS and MEMS compatibility.

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Rao, L. LRajeswara. "Design, Fabrication and Characterization of Metal Oxide Semiconductor Based MEMS Gas Sensors for Carbon Monoxide Detection". Thesis, 2017. https://etd.iisc.ac.in/handle/2005/4788.

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In recent years, intense efforts have been made towards the development of miniaturized gas-sensing devices for hazardous gas detection. Carbon monoxide, which is a result of incomplete combustion, is a colourless, odourless, poisonous, explosive and highly toxic gas. It binds with haemoglobin to form carboxyhemoglobin, which reduces the oxygen-carrying capacity of blood and, finally, leads to death. Hence, there is a need to develop a portable and cost-effective gas senor to detect low concentrations of CO gas. MEMS-based metal oxide semiconductor gas sensors offer several advantages compared to conventional optical and electrochemical techniques, such as compact size, low power consumption, quick response, high-temperature stability and low cost for mass production. However, a high-temperature is required for the optimum performance of metal oxide semiconducting gas sensors and such temperatures can be achieved with microheaters. The present thesis work deals with the design, fabrication and characterization of a MEMS gas sensor for the detection of low concentrations of carbon monoxide gas. The work is focused on five specific objectives: a) growth and characterization of sensing film; b) sensitivity enhancement using noble metal additives and nanowire structures; c) design, fabrication and characterization of microheaters; d) development of microhotplate integrated MEMS gas sensor; e) gas sensor packaging. The investigations undertaken are as follows: Titanium dioxide thin film sensing material is deposited using DC magnetron sputtering. The deposition conditions are optimized to obtain stoichiometric TiO2 thin films and are characterized for carbon monoxide gas detection. The influence of the operating temperature, annealing temperature, thin film thickness and the interdigitated electrode geometry on the sensor response is investigated. The TiO2 thin film sensor (annealed at 800 °C) shows a high response (79.5 %) to CO gas and a low response (<23%) to other reducing and oxidizing gases at 400 °C. It is observed that the sorption is completely reversible and the response and recovery times are of the order of 50 and 120 sec respectively. Noble metal additives such as Au, Pt, and Pd are decorated on the TiO2 surface to enhance the sensitivity and selectivity of the TiO2 thin film gas sensors. The pristine TiO2 thin film gas sensor (annealed at 400 °C) is found to exhibit a detectable response only when the operating temperature is above 300 °C; below this temperature there is no detectable change in resistance in the presence of 5000 ppb of CO gas. The response is found to increase with the operating temperature and it exhibits a maximum response of 58.6 % at 400 °C. The surface-modified TiO2 thin film based gas sensor shows a remarkable response event at 100 °C. The Au-TiO2 and Pt-TiO2 thin film gas sensor has been found to exhibit a maximum response of 83.46 and 79.64 % at 200 and 250 °C respectively, whereas, the Pd-TiO2 thin film gas sensor exhibits a n to p transition above 150 °C. TiO2 nanowires are synthesized using hydrothermal processes and are characterized for the detection of low concentrations of carbon monoxide gas. The TiO2 nanowire-based gas sensor shows a detectable change in its resistance even at 150 °C and its response is found to increase with the temperature. At 400 °C, the sensor is found to exhibit a maximum response of 80 % for 5000 ppb of CO. Further, under the same operating conditions, the sensor is found to exhibit a remarkable change in its resistance (a response of 5.6 %) for 100 ppb of CO. The response and recovery times of the sensor are of the order of 18 and 27 s respectively. Microheaters are designed and simulated using the CoventorWare MEMS design and analysis tool to optimize the geometry of the microheater structure for uniform temperature distribution and low power consumption. Low resistive molybdenum thin films are deposited for high temperature microheater applications. The molybdenum microheaters are fabricated and their electro-thermo-mechanical characteristics are studied. The microheater membrane stability is analyzed by measuring its deformation under high thermal stresses using an optical profilometer. The microheater response is characterized in both pulsed and constant temperature modes of operation; it is found to exhibit a negligible resistance drift after 600 hours of continuous operation, indicating its long-term thermal and mechanical stability. The response and recovery times are in the order of a few milliseconds (19 and 34 ms), which make them suitable for gas-sensing applications. Finally, microhotplate integrated MEMS gas sensors are fabricated, packaged and characterized for carbon monoxide gas detection at elevated temperatures (250 to 700 °C). The sensitivity, selectivity, repeatability and response and recovery times of the miniaturized MEMS gas sensors are investigated. The developed MEMS gas sensor is found to exhibit a high sensitivity and selectivity to CO gas compared to the TiO2 thin film based gas sensor. It shows a highest response of 96.14 % for 5000 ppb of CO and a minimum response (< 28%) to other reducing and oxidizing gases at 550 °C optimized temperatures. The MEMS gas sensor is found to exhibit quick response and recovery times (9 and 21 s) compared to thin film-based gas sensors (50 and 120 s).

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32

Khater, Mahmoud Elsayed. "Use of Instabilities in Electrostatic Micro-Electro-Mechanical Systems for Actuation and Sensing". Thesis, 2011. http://hdl.handle.net/10012/6398.

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This thesis develops methods to exploit static and dynamic instabilities in electrostatic MEMS to develop new MEMS devices, namely dynamically actuated micro switches and binary micro gas sensors. Models are developed for the devices under consideration where the structures are treated as elastic continua. The electrostatic force is treated as a nonlinear function of displacement derived under the assumption of parallel-plate theorem. The Galerkin method is used to discretize the distributed-parameter models, thus reducing the governing partial differential equations into sets of nonlinear ordinary-differential equations. The shooting method is used to numerically solve those equations to obtain the frequency-response curves of those devices and the Floquet theory is used to investigate their stability. To develop the dynamically actuated micro switches, we investigate the response of microswitches to a combination of DC and AC excitations. We find that dynamically actuated micro switches can realize significant energy savings, up to 60 %, over comparable switches traditionally actuated by pure DC voltage. We devise two dynamic actuation methods: a fixed-frequency method and a shifted-frequency method. While the fixed-frequency method is simpler to implement, the shifted-frequency method can minimize the switching time to the same order as that realized using traditional DC actuation. We also introduce a parameter identification technique to estimate the switch geometrical and material properties, namely thickness, modulus of elasticity, and residual stress. We also develop a new detection technique for micro mass sensors that does not require any readout electronics. We use this method to develop static and dynamic binary mass sensors. The sensors are composed of a cantilever beam connected to a rigid plate at its free end and electrostatically coupled to an electrode underneath it. Two versions of micro mass sensors are presented: static binary mass sensor and dynamic binary mass sensor. Sensitivity analysis shows that the sensitivity of our static mass sensor represents an upper bound for the sensitivity of comparable statically detected inertial mass sensors. It also shows that the dynamic binary mass sensors is three orders of magnitude more sensitive than the static binary mass sensor. We equip our mass sensor with a polymer detector, doped Polyaniline, to realize a formaldehyde vapor sensor and demonstrate its functionality experimentally. We find that while the static binary gas sensor is simpler to realize than the dynamic binary gas sensor, it is more susceptible to external disturbances.

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33

逄宜哲. "Research on Nano CMOS MEMS Gas Sensor". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/x63z9d.

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碩士
國立彰化師範大學
機電工程學系
98
Abstract This study proposes two different types of CO gas sensors, one of the ion sensor using field effect transistors (Ion Selective Field Effect Transistor, ISFET) to carry out carbon monoxide gas sensor manner, and its interface circuit technology and design combined with the sensing element structure, integrated gas sensor chip is made. Carbon monoxide sensors based on Si (Silicon) as substrate, P-type polysilicon (P-poly Silicon) when the micro-heater resistance, N-type poly (N-poly Silicon) When the etch stop layer, the N-type polysilicon, the re-heating a thin layer of oxide growth, the sensing material SnO2 was deposited onto the electrodes after sol-gel formation to detect the structure of CO gas. When the micro-heater temperature resistance to provide work, the number detected in the ISFET Telecommunications (Vs) at different CO concentrations in different variations. We use the TSMC 0.35μm CMOS 2P4M standard process and the production design process, after carbon monoxide sensors, ISFET amplifier circuit through the small amount of input and output voltages are different, but the actual measured results, as expected, did not significantly sensor signal, for sensing the gas from the electric sensor chip, the sensor out of the telecommunications insensitive and beating No. Although a large volume of design that we can try to clear the mechanism of the charge, the charge will reflect the volume after the measurement, the re- set to zero, in order to improve its telecommunications number of sensor in order to avoid signal saturation. III Another model for the resistance of carbon monoxide gas sensor, which is designed to honeycomb sensing electrode Finger type, using standard TSMC 2P4M 0.35um process of the metal layer Metal1 as Metal Mask, and to Metal4/Via34/Metal3/Via23/Metal2 level as a series of metal sensing electrode, and by P-type polysilicon (P-poly Silicon) when the micro-heater resistance 4.2kΩ, to provide heating power 120uW, the sensing material SnO2 was deposited onto the electrodes after sol-gel formation to detect CO gas, CO gas molecules when the sensor falls within the region, the adsorption on the sensor electrode, making electrode plate and the resistance value between electrodes changed, the corresponding measurements The sensitivity to the smallest resistor is 0.08%, while the CO concentration corresponding to the minimum limit of 4ppm the following. Keyword : Carbon monoxide、micro-heater、sol-gel、SnO2、ISFET.

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34

Ting-ChiaWeng i 翁梃嘉. "Bifacial Sensing Sides SnO2 MEMS Gas Sensor". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/5qu8ds.

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Shih, Ching-Wen, i 史景文. "Research on Sol-Gel CMOS MEMS Gas Sensor". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/90138855830225953062.

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碩士
國立彰化師範大學
積體電路設計研究所
99
Abstract Because of the rapid industrial and technological development, air pollution was getting worse. People increase the demand for gas sensors day by day.　Nowadays many researches study for sensors, the application of gas sensors is increasingly being used. In recent years, along with micro-electromechanical system (MEMS) technology progressed so fast that the bulky and high cost production machinery could be implemented in a small chip. The CMOS MEMS chip not only could reduce the cost of production and reach produce to short and small volume, but also could has better performance than the traditional machine because CMOS process could integrate the circuit and MEMS structure. This thesis proposes a CMOS MEMS CO gas sensor which is fabricated by TSMC (Taiwan Semiconductor Manufacturing Company)　0.35μm 2P4M-CMOS process and wet etching of post process.　We design a CMOS MEMS gas sensor and use poly1 to be the micro-heater for providing the working temperature, and use metal2 and metal4 to be the electrode A, metal3 to be the electrode B. Finally we use the sol-gel method to produce tin oxide sensing film for sensing carbon monoxide. In this thesis, we will introduce the post-process and CMOS process and production of sensing film by using sol-gel method. Finally we analyze the sensitivity of carbon monoxide by using CMOS MEMS gas sensor, and do the experimentation for relative humidity (%RH). Keywords: Gas sensor, Tin oxide, CMOS MEMS, Carbon monoxide

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Zheng, Yu-Zhan, i 鄭宇展. "Study of The SnO2:Ni MEMS gas sensor". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/t8q6ay.

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碩士
國立雲林科技大學
電子工程系
106
SnO2 material has many excellent characteristics and can detect most gases, but the disadvantage is that it cannot distinguish the type of gas. In this study, SnO2 is used as a sensing material and surface-doped Ni-resistive resistive gas sensor. First, the indoor gases of volatile organic compounds (VOC) and formaldehyde (HCHO) are distinguished and the best parameters are found, and finally compared with other gases. In this research process, Si3N4/ SiO2 is first deposited by LPCVD as an insulating layer on six inch wafer P-type (100). The use of E-Gun Pt / Ti deposited it up and define the patterned as electrode, micro heater and electric film group, then use RF SnO2 as the sensing layer deposited on the electrode, then the use of E-Gun, the nickel metal respectively by 3nm, 5nm, 10nm and 20nm of different thickness deposited on the sensing layer as the catalyst layer. Then ICP-DRIE is used to etch a thermal insulation slot at the bottom of the micro heater to form a suspension structure to complete the sensor element. Finally, the best result of this experiment is Ni (3nm) /SnO2, which is annealed for 10 minutes at atmospheric temperature for 400℃, and at a certain power 136.9mW, at the operating temperature of 250℃, the concentration of VOC and HCHO is 80ppb. HCHO has super high response rate of 74% and has good selectivity. More detailed information on the research will be discussed in this paper. Keyword：Indoor air quality、SnO2、Transition metal、formaldehyde、VOC、gas sensor

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Wang, Chia-Chuan, i 王嘉傳. "A gas flow control system integrating MEMS flow sensor". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/17698419680003583299.

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碩士
國立交通大學
工學院半導體材料與製程設備學程
101
Gas control in the electronics industry and the semiconductor manufacturing are very important key process. Commonly in gas flow control system the key product is use mass flow controller to control flow rate generally called MFC (Mass Flow controller).Mass flow controller is combined the flow sensor, proportional valve, PID controller device, but when any device needs to re-calibration or maintenance and change the specifications in the production line or re-design will cause a trouble and inconvenience. This thesis focused on use new generation of MEMS fabrication process flow sensor to replace the traditional thermal flow sensor, and introduce how to combine independent proportional valve, PID controller, PLC and HMI to do a like MFC function flow control system. Because each component are independent modular system, so not only more convenient to maintenance and calibration, and via the independent modular components can be separately applied to various gas flow control system, and can be effectively used in industrial equipment.

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Chien-HuaPeng i 彭建華. "Zinc Oxide Nanorods MEMS Gas Sensor with Blue Light Enhancement". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/y84kng.

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Chia-HuiLu i 呂嘉輝. "Zinc Oxide Thin Film MEMS Gas Sensor with Different Structure". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/na42xn.

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李文傑. "Research on Magnetic Catalytic Application of CMOS MEMS Compatible Gas Sensor". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/48624793484013899440.

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碩士
國立彰化師範大學
機電工程學系
101
Due to the environment pollution issues and industrial demands, many researches are committed to develop a high-performance gas sensor, which can be used to detect toxic and explosive gases. CO gas sensor is one of the important research topics utilized to detect CO concentrations in environments. In this research, a gas sensor with mesh stacked electrodes mainly by using 2P4M 0.35μm CMOS MEMS IC technology of TSMC to detect the CO concentration with combination of sensing circuit. SnO2 doped with Fe3O4 is taken as sensing material and a Magnetic-Catalyst is proposed in this research. The sensitivities of gas sensing are enhanced through different angle and magnitude of magnetic field. The experiment results reveal that when the magnitude of magnetic field decreases, the sensitivities declines. Staying in horizontal magnetic field surroundings under the condition of 12 Gauss, the highest sensitivity of gas sensor 1.73%/ppm is obtained and is 7 times higher than the sensitivity of gas sensor without Magnetic-Catalyst.

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Chang, Shu-Yu, i 張書瑜. "Research and development of gas sensor based on CMOS-MEMS process". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/427w3z.

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碩士
國立交通大學
電控工程研究所
107
In this study, a gas sensor was successfully developed using the COMS-MEMS process. The materials of the micro-heater platform were not required to be coated with precious metals by the post-process, and were completely compatible with the standard COMS process. After the wafer is out of the fab, the devices have been followed by a deep reactive ion etching(DRIE) and deposited sensing film by liquid phase deposition method. Different from the traditional way, the catalyst was successfully doped on the sensing film by using printing technique. Because the COMS-MEMS process can significantly reduce the uncertainty caused by the process, it can improve the yield and reduce the cost and sensor area. The micro-heater platform use tungsten as a micro-heater. When the temperature is operated at 400 °C, the heater uniformity can be controlled within 10 degrees and the power consumption is about 40mW, which is in line with the original simulation goal of this study. Before measuring the carbon monoxide gas, doping the palladium chloride aqueous solution onto the sensing film, and adjusting the number of printing to achieve a quantitative effect. The concentration of carbon monoxide gas is 50PPM, 100PPM, 150PPM to 200PPM, respectively. The sensitivity and resolution of the sensor are recorded under four different carbon monoxide concentrations. Also compare the number of times of printing to one to five times the effect of gas reaction. It is known from the experimental results that the number of times of printing can greatly increase the sensitivity regardless of the number of times of printing. In terms of gas resolution, the best result is obtained when printing the catalyst four times, the slope is 0.134, and the result is superior to CCS801 on the market.

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Lee, Mu-Tsun, i 李牧錞. "The Study of Fabrication and Gas Characteristics of MEMS-based Benzene Gas Sensor Incorporated in WO3 Films". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/469ggt.

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碩士
國立臺北科技大學
冷凍空調工程系所
94
Benzene （C6H6）is a highly important commercial chemical due to its chemical activity, high purity and relative cheapness. It is an organic compound that causes serious concerns in environmental health due to its toxicity and carcinogenic properties, even at low concentrations. The OSHA（Occupational Safety & Health Administration）has established a permissible Time-Weighted-Average exposure limit of 1 ppm. This paper describes the preparation of tungsten trioxide（WO3）thin films by the reactive RF magnetron sputter. The primary deposition parameters that influence the microstructure, chemical and electrical properties of WO3 thin films formed by reactive magnetron sputtering are substrate temperature, Ar/O2 concentration ratio, total pressure, and RF power. The films are then stabilized by annealing in dry air. The platinum catalytic filter were developed to enhance the sensitivity of tungsten trioxide to benzene. The characterists of their structural properties were presented by means of XRD measurements and the film morphology by the SEM microscope. The sensors were operated at the temperature range from 250 to 350℃ to analyse the effect of working temperature on their response. The present sensor shows good speed of response and highly detective limit of concentration at 350℃.

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43

張峻銘. "Analysis of MEMS Gas Flow Sensor with Pressure Drop Induced by Perforated Plates". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/94346204256148272795.

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JIONG, HENG LU, i 盧炯亨. "Research on Electromagnetic Field Effect of Novel Tip Type CMOS-MEMS Gas Sensor". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/97003694183737911240.

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碩士
國立彰化師範大學
機電工程學系
102
In this research, we proposed a novel electromagnetic coupling-catalyst of CMOS-MEMS gas sensor. The conventional gas sensor with finger type electrode enhances the sensitivity by sensing material. A new gas sensor with the tip-type electrode achieve high electric field in a standard CMOS process. The sensing material SnO2/Fe3O4 coated on sensing structure was catalyzed by Electromagnetic coupling. The research focus on electric field catalysis, Magnetic-catalysis and Electromagnetic coupling-Catalyst. We apply 6V~30V on each tip-type electrode which the distance between the tip-type electrodes is 8.5m. The sensitivity of proposed monoxide sensor with electric field catalysis is 1.72 times higher than the sensitivity of gas sensor without electric field catalysis. On the other hand, when the magnetic field and electric field are parallel, the sensitivity would increase. The sensitivity of sensors can be 1.94 times higher than the sensitivity of gas sensor without magnetic-catalyst. Staying electromagnetic coupling field, the highest sensitivity of gas sensor 0.68 %/ppm is obtained and is 2.62 times higher than the sensitivity of gas sensor under 30 V electric field catalysis. The experimental measurement shows a new approach of gas sensing enhancement with electromagnetic coupling catalyst, and it is applicable for an ultra-low power CO sensor with high sensitivity.

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45

Emadi, Tahereh Arezoo. "Development of a MEMS chemicapacitor polymer-based gas sensor on a temperature controlled platform". 2011. http://hdl.handle.net/1993/4815.

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Grain storage is an essential part of the food production chain. Therefore, pre- venting grain deterioration is a key issue in a grain storage system. There are several causes for spoilage, all resulting in grain quality and quantity loss. One approach to detect incipient spoilage is by detecting the produced volatiles. In the past, many sensors for detecting volatiles have been developed and are used in industry. However, most of the commercial gas sensors are bulky with high power consumption, mainly limited in range of operating temperature, or require a restricted control over temperature and humidity. This thesis describes the design, fabrication and evaluation of a gas sensor capable of detecting volatiles and considers the potential use of polymer- based sensors. Conductive polymer-based sensors have been reported sensitive to a wide range of volatiles but are commonly evaluated under a controlled environment. Conventional sensor reproducibility and repeatability are also a concern due to the difficulties associated with polymer composite film preparation. In addition, current studies have not fully explored sensor properties in response to humidity, a common factor in any environment, and a variable parameter in grain storage facilities. Moreover, these sensors suffer from ambient temperature dependency as they work based on partitioning mechanism. To enhance sensor performances and eliminate the temperature dependency, a new sensor structure is proposed. The new design uses standard lithography process to fabricate a thermally isolated cantilever containing interdigitated electrodes and a micro-heater to efficiently heat and maintain a constant temperature throughout the interdigitated electrodes. This structure eliminates sensor response drifts caused by ambient temperature variations. Capacitive measurements are performed as the means of volatile detection, which simplify the use of polymers due to the absence of conductive filler and the challenges associated with it. Frequency spectroscopy provides additional information regarding the presence of volatiles compared to conventional resistive sensors, since mechanisms other than swelling are involved. Moreover, frequency and temperature modulations can be employed to further enhance sensor performance, enabling the use of a reduced number of sensors in a sensor array.

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46

Chen, Yen-Cheng, i 陳彥呈. "A CMOS MEMS Gas Sensor Using Monolayer Protected Gold nanoClusters Coating On Three-Dimensional interdigitated Electrodes". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/37365153714313787817.

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碩士
國立臺灣大學
生醫電子與資訊學研究所
100
In this research, we developed a chemiresistive gas sensor for micro gas chromatography system. The sensing material, monolayer protected gold nano-cluster (MPC), was coated onto the three dimensional interdigitated electrodes (3D IDEs) of the sensor. The measuring principle of this sensitive material is based on the impedance variation corresponding to different gas concentrations. This chemiresistive sensor was realized by using CMOS-MEMS fabrication process is based on TSMC 0.35μm 2P4M (2 polysilicon 4 metal) process and post process. The device was completed after spreading the sensitive material MPC on its surface. The 3D IDEs are composed by the first and third layer of the metal on one side and the second and forth layer of the metal on the other side. Our 3D IDEs not only increased the sensing surface area at a given chip area but also decreased the gap distance between electrodes to 1μm. This reduced gap distance increased the sensitivity of the sensor as well as lowered the resistance of the deposited sensing material. In this research, the great linearity and sensitivity of the sensor were demonstrated with three compounds (Octane, Butanol, and Toluene) at different concentrations in the range of 30ppm to 5000ppm and manifested the good linearity and sensitivity. Our sensor with exceptional reliability was also demonstrated by a prolonged testing over three months with minimal drift.

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47

Yan, Bo-Kai, i 顏伯凱. "A CMOS MEMS capacitive tactile sensor with polymer gap and metal sensing electrode". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/50126597817918409228.

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Jang, Drung-Han, i 詹宗翰. "The Study of MEMS-based Ozone Gas Sensor Incorporated in WO3 Films and its Application in Effective Ventilation". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/3jjhyv.

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碩士
國立臺北科技大學
能源與冷凍空調工程系碩士班
96
This paper describes the preparation of tungsten trioxide（WO3）thin films by the reactive RF magnetron sputter for the ozone sensor. The primary deposition parameters that influence the microstructure, chemical and electrical properties of WO3 thin films formed by reactive magnetron sputtering are substrate temperature, Ar/O2 concentration ratio, total pressure, and RF power. The films are then stabilized by annealing in dry air. The platinum catalytic filter was developed to enhance the sensitivity of tungsten trioxide to benzene. The characteristics of its structural properties were presented by means of XRD measurements and the film morphology by the SEM microscope. The sensors were operated at the temperature range from 250 to 350℃ to analyze the effect of working temperature on their response. On the other hand, at modern time use of the photogravure press, tabulating machine and other business machines produce a lot of new indoor air pollution and cause the influence of the different aspects on the health. The result that comes down for a long time, because indoor air quality is bad, causes the sick building syndrome (SBS) and building related illness. In ventilated interior environments of buildings, the determination of air-flow velocities, temperatures and concentrations of pollutants is required to evaluate comfort conditions and indoor air quality. This thesis also investigates the effective ventilation by computational fluid dynamics（CFD）methods. The indoor air quality is determined by computing the mean age of air and concentration of ozone in a specified office. The results from the present study can be used to manufacture a practical MEMS-based ozone sensor and corporate it into the building HVAC control system for the effective ventilation in impelling the ozone pollution.

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Huang, Yen-Chi, i 黃彥期. "Design, Implementation and Measurement of a MEMS Type Gas Sensor with SnO2 Sensing Film Prepared by Liquid Phase Deposition Method". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/10803727673561292010.

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碩士
國立交通大學
電控工程研究所
99
In this thesis, a micro H2S gas sensor with liquid phase deposition (LPD) based sensing film on the micro hotplate, was successfully implemented by utilizing MEMS fabrication technology. Versatile advantages including miniaturized structure, low-power consumption, high-sensitivity and high-yield production were achieved by the proposed method. Additionally, cantilever bridge structure design allows shorter heating time with low power supply to reach required working temperature. The thermal response time constant of proposed structures shows more than 50 times faster than the un-suspended structures under room temperature. Moreover, 2-types of heater designs, including serpentine and annular structures, were tested for heat conduction performance comparison. By applying the proposed LPD method, complex equipments with vacuum chamber were no longer needed for high-performance sensing film fabrication. Finally, related heat and gas response characterization for micro-heater and thin-film structure were measured and discussed, respectively.

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Graf, Alexander. "Entwicklung eines miniaturisierten Ionenfilters und Detektors für die potentielle Anwendung in Ionenmobilitätsspektrometern". Doctoral thesis, 2014. https://tud.qucosa.de/id/qucosa%3A28629.

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Die Ionenmobilitätsspektrometrie ermöglicht eine selektive Detektion von niedrigkonzentrierten Gasen in Luft. Darauf beruhende Analysegeräte können verhältnismäßig einfach umgesetzt werden und in vielfältigen mobilen Einsatzszenarien wie der Umweltanalytik Anwendung finden. Die vorliegende Dissertation gibt einen Überblick über die Grundlagen der Ionenmobilitätsspektrometrie und setzt die funktionellen Teilkomponenten Ionenfilter und Ionendetektor mit Mikrosystemtechniken um. Dafür werden Möglichkeiten aus dem Stand der Technik vorgestellt und eine für die Umsetzung optimale Variante identifiziert. Ein Ionenfilter basierend auf der Differenzionenmobilitätsspektrometrie zeigt diesbezüglich ein sehr geeignetes Skalierungsverhalten. Zur Integration in einen Demonstrator-Chip wird ein neuartiges Bauelementkonzept verfolgt, mit technologischen Vorversuchen untersetzt und erfolgreich in einen Gesamtherstellungsablauf überführt. Mit Hilfe von weiterführenden analytischen Untersuchungen werden spezifische Phänomene bei der elektrischen Kontaktierung der verwendeten BSOI-Wafer als Ausgangsmaterial hergeleitet und Empfehlungen zur Vermeidung gegeben. Der Funktionsnachweis der Teilkomponente Ionendetektor wird anhand von hergestellten Demonstrator-Chips und mit Hilfe eines entwickelten Versuchsaufbaus begonnen. Es werden die weiteren Schritte zum Nachweis der Gesamtfunktionalität abgeleitet und festgehalten. Auf Basis des umgesetzten Bauelement- und Technologiekonzepts und der vorliegenden Ergebnisse, wird das entwickelte und realisierte Gesamtkonzept als sehr aussichtsreich hinsichtlich der favorisierten Verwendung als Teilkomponente eines miniaturisierten Ionenmobilitätsspektrometers eingeschätzt.:1 Einleitung 1.1 Motivation und Zielstellung 1.2 Aufbau und Gliederung der Arbeit 2 Grundlagen zur Ionenmobilitätsspektrometrie 2.1 Grundprinzip der Ionenmobilitätsspektrometrie 2.2 Anwendungsfelder und Substanzen 2.3 Grundlagen der Ionenbewegung 2.4 Ionenquellen 2.4.1 Ionisation mittels radioaktiver Strahlungsquellen 2.4.2 Photoionisation 2.4.3 Weitere Ionenquelle 2.4.4 Vergleich von Ionenquellen 2.5 Ionendetektion 2.6 Bewertungskriterien Ionenmobilitätsspektrometer 3 Stand der Technik Ionenfilter 3.1 Überblick und Einteilung Ionenfilter 3.2 Zeitaufgelöste Detektion 3.3 Ortsaufgelöste Detektion 3.4 Differenz der Ionenmobilität 3.4.1 Differenzionenmobilitätsspektrometrie 3.4.2 Transversal Modulation Ionenfilter 3.5 Sonstige Filterrealisierungen 3.5.1 Ionenfilter mit Gegengasströmung 3.5.2 Travelling Wave Filter 3.6 Vergleich Ionenfilter für ein miniaturisiertes Ionenmobilitätsspektrometer 3.7 Konkretisierte Zielstellung der Arbeit 4 Konzeptionelle Vorarbeiten 4.1 Modellbildung und Dimensionierung des Ionenfilters 4.1.1 Allgemeine Lösung der Bewegungsgleichung 4.1.2 Lösung für den Spezialfall mit Rechteckanregung 4.1.3 Randbedingungen bei der Filterauslegung 4.1.4 Elektrische Simulation des Ionenfilters mit diskreten Elementen 4.1.5 Auslegung eines miniaturisierten Ionenfilters 4.2 Modellbildung und Auslegung des Ionendetektors 4.3 Ableitung eines relevanten Parameterraums 5 Voruntersuchungen und Empfehlungen zur technologischen Umsetzung 5.1 Herleitung des Bauelementkonzepts 5.1.1 Konzept 1 – Planar-Aufbau 5.1.2 Konzept 2 – Sandwich-Struktur 5.1.3 Konzept 3 – Erweiterte Tiefenstruktur 5.1.4 Ableitung des umzusetzenden Bauelementkonzepts 5.2 Konzept zur Herstellung der Ionenkanäle 5.2.1 Nasschemische Siliziumstrukturierung mit TMAH 5.2.2 Trockenchemische Siliziumstrukturierung mit DRIE 5.2.3 Durchführung und Ergebnisse des Vorversuchs 5.2.4 Schlussfolgerung und Ausblick für die Herstellung der Elektrodenkanäle 5.3 Konzept zur Realisierung der Elektrodenkontakte 5.3.1 Möglichkeiten zur Kontaktierung der Elektrodenstrukturen 5.3.2 Verfahren und Materialien für das Erzeugen von Isolationen 5.3.3 Verfahren und Materialien für das Abscheiden von Metallen 5.3.4 Besonderheiten beim Metall-Halbleiter-Kontakt 5.3.5 Ableiten eines Technologieablaufs und Durchführung eines Versuchs zur Herstellung der Rückseitenkontakte 5.3.6 Elektrische Charakterisierung der Rückseitenkontakte 5.3.7 Ausblick zur weiteren Bewertung der Rückseitenkontakte 5.4 Überblick über relevante Waferbondverfahren 5.5 Konzept für die Aufbau- und Verbindungstechnik 5.6 Integration der Vorversuche in ein erweitertes Bauelementkonzept 6 Bauelementauslegung für ein Ionenmobilitätsspektrometer 6.1 Voruntersuchungen für die Bauelementdimensionierung 6.1.1 Simulation des elektrischen Verhaltens mit einem erweiterten Ersatzschaltbild 6.1.2 Dimensionierung des Einströmbereichs und des Vorfilters 6.2 Zusammenfassung der Voruntersuchungen und Ableitung von Designvarianten 7 Technologische Umsetzung und Untersuchung der Kontaktproblematik 7.1 Umsetzung Filter- und Detektordemonstrator 7.1.1 Auswahl der Metallisierung 7.1.2 Erstellen eines detailliertern Gesamttechnologieablaufs 7.1.3 Verifikation des umgesetzten Herstellungsprozesses an den realisierten Demonstrator-Chips 7.2 Untersuchung Metall-Halbleiter-Kontakt 7.2.1 Untersuchung Metall-Halbleiter-Interface 7.2.2 Einfluss des Ausheilschritts auf das Kontaktverhalten 7.2.3 Untersuchung des Dotierungs- und Leitfähigkeitsprofils 7.2.4 Herleitung einer möglichen Ursachenkette für die Bor-Kontamination 7.2.5 Gegenprüfung der Ursachenkette und Schlussfolgerung 7.3 Zusammenfassung Technologieablauf 8 Charakterisierung der Teilkomponenten 8.1 Konzeptionelle Vorarbeiten zum Versuchsaufbau 8.1.1 Methoden zur Testgaserzeugung 8.1.2 Integration des IMS-Chips in die Gasversorgung 8.1.3 Elektronikanbindung 8.2 Versuchsaufbau und Versuchsplanung 8.2.1 Beschreibung Versuchsaufbau 8.2.2 Planung der Versuche für Bewertung Ionendetektor 8.2.3 Planung der Versuche für Bewertung Ionenfilter 8.3 Versuche und Bewertung Ionendetektor 8.3.1 Versuchsdurchführung 8.3.2 Auswertung Ionendetektor 8.4 Zusammenfassung und Ausblick der Charakterisierung 9 Zusammenfassung und Ausblick Literaturverzeichnis

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