Dissertationen zum Thema „Gas microsensors“

Résumé indisponible
This PhD work is dedicated to investigate potentialities of phthalocyanines materials to realize a Quartz Crystal Microbalance (QCM) sensor for Benzene, Toluene and Xylenes (BTX) detection in air. The goal is to develop a sensor-microsystem capable of measuring BTX concentrations quantitatively below the environmental guidelines with sufficient accuracy. To achieve these objectives, our strategies mainly focused on experimental works encompassing sensors realization, sensing material characterizations, development of gas-testing facility and sensor testing for different target gases. One of the main aims is to identify most appropriate phthalocyanine material for sensor development. After comparative sensing studies, tert-butyl-copper phthalocyanine based QCM device is found as most sensitive and detail metrological characteristics are further investigated. Results show repeatable, reversible and high magnitude of response, low response and recovery times, sub-ppm range detection limit, high resolutions and combined selectivity of BTX gases among common atmospheric pollutants. Special focus is given to understand the gas/material interactions which are achieved by (a) XRD and SEM characterizations of sensing layers, (b) formalization of a two-step adsorption model and (c) assessing extent of diffusion of target gas in sensing layer. At last, possible ageing of sensor and suitable storage conditions to prevent such effect are investigated

Increasing concern about the rapid escalation of environmental pollution has led to strong legislation to ensure, for example, that the emission of pollutants from vehicles and industries is controlled to an acceptable level. As a consequence, there has been a rapid expansion of research into developing more efficient and low-cost gas monitoring systems. Currently, commercial solid-state atmospheric gas detection systems are based on one sensor for each gas, while research systems are an array of sensors for the detection of multiple gases. In this research, techniques are developed whereby more than one gas is detected using a single resistive gas sensor. A novel modulated temperature technique was used to enhance the selectivity of the resistive SnO2 gas sensor. Fast Fourier transforms was used to extract the Fourier coefficients. These in turn were used as input to neural networks for training and subsequently for prediction purposes. The result has shown that a single doped SnO2 resistive microsensor can be used to classify binary gas mixture in air. The research objectives have been fulfilled in that a novel way in detecting the components and the concentration level of a binary gas mixture was developed. Additionally, a low-cost low-power intelligent gas monitoring system was designed. This included the design of a novel temperature/thermometer circuit.

Nous proposons dans le cadre de ce travail de thèse, une nouvelle approche de la détection non invasive de l’alcoolémie sanguine à l’aide de microcapteurs d’éthanol à base de SnO2. Cette méthodologie se base sur une détection indirecte de l’alcoolémie sanguine par une mesure des vapeurs d’éthanol émises par la perspiration cutanée suite à une consommation d’alcool. Afin de valider cette approche, il a fallu dans un premier temps démontrer la pertinence et la faisabilité de cette méthodologie de détection par la réalisation d’essais cliniques pilotes en collaboration avec une équipe médicale d’étude pharmacologique du CPCET Marseille. Les différentes mesures du taux d’éthanol réalisées dans les fluides biologiques tels que le sang et l’air expiré ont pu être précisément corrélées avec les mesures de vapeurs d’éthanol réalisées à travers la perspiration à l’aide de trois microcapteurs de gaz commerciaux à base d’oxydes métalliques intégrés à un bracelet. Ces dispositifs ont l’avantage d’être sensibles mais pas sélectifs à la nature du gaz détecté. Durant ces travaux, des couches sensibles de SnO2 ont été déposées par pulvérisation cathodique RF magnétron réactive sur un transducteur breveté par notre équipe, intégrant trois capteurs sur une même puce. L’optimisation des paramètres de dépôt et les analyses structurales des couches de SnO2, nous ont permis de réaliser un multicapteur d’éthanol démontrant des performances sous éthanol ; en termes de sensibilité sous atmosphère humide, de répétabilité et de temps de réponses et de recouvrement ainsi que du point de vue sélectivité
A new approach of a noninvasive detection of blood alcohol concentration using ethanol microsensors based on SnO2 Is developed in this work. The methodology is based on an indirect detection of blood alcohol concentration by measuring the ethanol vapor emitted through the skin perspiration after alcohol consumption. In order to validate this approach, first we demonstrated the relevance and the feasibility of this detection method by carrying out pilot clinical trials in collaboration with a medical team of pharmacological study of CPCET Marseille. The different measurements of the ethanol concentration carried out in biological fluids such as blood and exhaled air could be precisely correlated with the measurements of ethanol vapors performed through the perspiration using three commercial gas microsensors based on metal oxides integrated into a bracelet. . These devices have the advantage of being sensitive but not selective to the nature of the gas detected. During this thesis work, sensitive layers of SnO2 were deposited by reactive magnetron RF sputtering on a transducer patented by our team, integrating three sensors on the same chip. The optimization of the deposition parameters and the structural analyzes of the SnO2 layers, allowed us to develop an ethanol multi-sensor demonstrating performances under ethanol; in terms of sensitivity on humidity, repeatability and response and recovery times as well as from the point of selectivity

A la différence de la pollution de l’air extérieur, celle de l’air intérieur est restée relativement peu étudiée jusqu’au début des années 2000. Pourtant, nous passons en moyenne 85 % de notre temps dans des environnements clos (domicile, bureaux, transports…) dans lesquels nous sommes exposés à de nombreux polluants. De nombreuses études ont montré que la mesure de la concentration du dioxyde de carbone, permet d’évaluer le confinement de l’air intérieur. Pour mesurer les polluants, nous pouvons distinguer les analyseurs et les microcapteurs, avec chacun ses avantages et ses inconvénients. Dans le cas de la qualité de l’air intérieur, les microcapteurs de type résistif paraissent comme la solution la plus appropriée, de par leur faible coût, leur haute sensibilité, leur miniaturisation possible et leur faible consommation. Le phénomène de détection s’établit sur la variation de la résistance électrique de l’élément sensible en réponse à un taux d’adsorption du gaz. Mes travaux de recherche se sont concentrés sur l’étude de la couche sensible. Nous avons utilisé la méthode de dépôt par screen printing, technique simple, rapide et peu coûteuse. La structure cristalline et la morphologie ont pu être déterminées ainsi que l’identification des substances chimiques présentes dans nos matériaux suivant des techniques de caractérisations physico-chimiques. Nos résultats ont montré que les capteurs réalisés à base de La2O2CO3 et de BaTiO3, respectivement, présentent de bonnes performances, avec une forte sensibilité au CO2, et un bon taux de répétabilité
Unlike outdoor air pollution, indoor air pollution remained relatively understudied until the early 2000s. However, we spend on average 85% of our time in closed environments (home, offices, transport, etc. in which we are exposed to many pollutants. Numerous studies have shown that measuring the concentration of carbon dioxide makes it possible to assess the confinement of indoor air. To measure pollutants, we can distinguish between analyzers and microsensors, each with its advantages and disadvantages. In the case of indoor air quality, resistive type microsensors appear to be the most appropriate solution, due to their low cost, high sensitivity, possible miniaturization and low power consumption. The detection phenomenon is based on the variation of the electrical resistance of the sensitive element in response to a gas adsorption rate. My research work has focused on the study of the sensitive layer. We used the screen-printing deposit method, a simple, fast and inexpensive technique. The crystalline structure and the morphology could be determined as well as the identification of the chemical substances present in our materials according to physico-chemical characterization techniques. Our results showed that the sensors made from La2O2CO3 and BaTiO3, respectively, present good performances, with a high sensitivity to CO2, and a good repeatability rate

Cette thèse s’inscrit dans le cadre d’une cotutelle internationale entre l’Université de Bourgogne Franche-Comté en France et l’Université de Sherbrooke au Canada. Elle porte sur le développement d'un biocapteur miniature pour la détection et la quantification de bactéries dans des milieux liquides complexes. La bactérie visée est l’Escherichia coli (E. coli), régulièrement mise en cause dans des épidémies d'infections alimentaires, et parfois meurtrière.La géométrie du biocapteur consiste en une membrane en arséniure de gallium (GaAs) sur laquelle est déposé un film mince piézoélectrique d’oxyde de zinc (ZnO). L'apport du ZnO structuré en couche mince constitue un réel atout pour atteindre de meilleures performances du transducteur piézoélectrique et consécutivement une meilleure sensibilité de détection. Une paire d'électrodes déposée sur le film de ZnO permet de générer sous une tension sinusoïdale une onde acoustique se propageant dans le GaAs, à une fréquence donnée. La face arrière de la membrane, quant à elle, est fonctionnalisée avec une monocouche auto-assemblée (SAM) d'alkanethiols et des anticorps anti-E. coli, conférant la spécificité de la détection. Ainsi, le biocapteur bénéficie à la fois des technologies de microfabrication et de bio-fonctionnalisation du GaAs, déjà validées au sein de l’équipe de recherche, et des propriétés piézoélectriques prometteuses du ZnO, afin d’atteindre potentiellement une détection hautement sensible et spécifique de la bactérie d’intérêt. Le défi consiste à pouvoir détecter et quantifier cette bactérie à de très faibles concentrations dans un échantillon liquide et/ou biologique complexe.Les travaux de recherche ont en partie porté sur les dépôts et caractérisations de couches minces piézoélectriques de ZnO sur des substrats de GaAs. L’effet de l’orientation cristalline du GaAs ainsi que l’utilisation d’une couche intermédiaire de Platine entre le ZnO et le GaAs ont été étudiés par différentes techniques de caractérisation structurale (diffraction des rayons X, spectroscopie Raman, spectrométrie de masse à ionisation secondaire), topographique (microscopie à force atomique), optique (ellipsométrie) et électrique. Après la réalisation des contacts électriques, la membrane en GaAs a été usinée par gravure humide. Une fois fabriqué, le transducteur a été testé en air et en milieu liquide par des mesures électriques, afin de déterminer les fréquences de résonance pour les modes de cisaillement d’épaisseur. Un protocole de bio-fonctionnalisation de surface, validé au sein du laboratoire, a été appliqué à la face arrière du biocapteur pour l’ancrage des SAMs et des anticorps, tout en protégeant la face avant. De plus, les conditions de greffage d’anticorps en termes de concentration utilisée, pH et durée d’incubation, ont été étudiées, afin d’optimiser la capture de bactérie. Par ailleurs, l’impact du pH et de la conductivité de l’échantillon à tester sur la réponse du biocapteur a été déterminé. Les performances du biocapteur ont été évaluées par des tests de détection de la bactérie cible, E. coli, tout en corrélant les mesures électriques avec celles de fluorescence. Des tests de détection ont été réalisés en variant la concentration d’E. coli dans des milieux de complexité croissante. Différents types de contrôles ont été réalisés pour valider les critères de spécificité. En raison de sa petite taille, de son faible coût de fabrication et de sa réponse rapide, le biocapteur proposé pourrait être potentiellement utilisé dans les laboratoires de diagnostic clinique pour la détection d’E. coli
This thesis was conducted in the frame of an international collaboration between Université de Bourgogne Franche-Comté in France and Université de Sherbrooke in Canada. It addresses the development of a miniaturized biosensor for the detection and quantification of bacteria in complex liquid media. The targeted bacteria is Escherichia coli (E. coli), regularly implicated in outbreaks of foodborne infections, and sometimes fatal.The adopted geometry of the biosensor consists of a gallium arsenide (GaAs) membrane with a thin layer of piezoelectric zinc oxide (ZnO) on its front side. The contribution of ZnO structured in a thin film is a real asset to achieve better performances of the piezoelectric transducer and consecutively a better sensitivity of detection. A pair of electrodes deposited on the ZnO film allows the generation of an acoustic wave propagating in GaAs under a sinusoidal voltage, at a given frequency. The backside of the membrane is functionalized with a self-assembled monolayer (SAM) of alkanethiols and antibodies anti-E. coli, providing the specificity of detection. Thus, the biosensor benefits from the microfabrication and bio-functionalization technologies of GaAs, validated within the research team, and the promising piezoelectric properties of ZnO, to potentially achieve a highly sensitive and specific detection of the bacteria of interest. The challenge is to be able to detect and quantify these bacteria at very low concentrations in a complex liquid and/or biological sample.The research work partly focused on the deposition and characterization of piezoelectric ZnO thin films on GaAs substrates. The effect of the crystalline orientation of GaAs and the use of a titanium / platinum buffer layer between ZnO and GaAs were studied using different structural (X-ray diffraction, Raman spectroscopy, secondary ionization mass spectrometry), topographic (atomic force microscopy), optical (ellipsometry) and electrical characterizations. After the realization of the electrical contacts on top of the ZnO film, the GaAs membrane was micromachined using chemical wet etching. Once fabricated, the transducer was tested in air and liquid medium by electrical measurements, in order to determine the resonance frequencies for thickness shear mode. A protocol for surface bio-functionalization, validated in the laboratory, was applied to the back of the biosensor for anchoring SAMs and antibodies, while protecting the top side. Furthermore, different conditions of antibody grafting such as the concentration, pH and incubation time, were tested to optimize the immunocapture of bacteria. In addition, the impact of the pH and the conductivity of the solution to be tested on the response of the biosensor has been determined. The performances of the biosensor were evaluated by detection tests of the targeted bacteria, E. coli, while correlating electrical measurements with fluorescence microscopy. Detection tests were completed by varying the concentration of E. coli in environments of increasing complexity. Various types of controls were performed to validate the specificity criteria. Thanks to its small size, low cost of fabrication and rapid response, the proposed biosensor has the potential of being applied in clinical diagnostic laboratories for the detection of E. coli

碩士
逢甲大學
自動控制工程學系
102
The research develops self-assembled anodic titanium oxide arrays fabricated by anodization and combines the microheater and temperature sensor manufactured by the photolithography and life-off process of the micro-electro-mechanical system technology to selectively detect the CO and CHCl3 gas in room temperature. The advantages of the gas sensors combine anodic titanium oxide thin film, noble metal electrodes, microheater and temperature sensor in the chip have small volume, high stability, high sensitivity and accuracy. The TiO2 arrays fabricated by anodization can built different aspect ratio nanotubes, the inner diameter range is 22-110 nm and the length range is 1.21-1.91μm, by controlling the voltage and anodic time and have high porosity to promote the sensitivity of the gas sensing ability of the sensing film. The gas microsensor can keep the sensor in the best temperature by control the voltage of the microheater and detect the environment temperature by temperature sensor. Experimental results are analyzed to find the relationship between the CO and CHCl3 gas concentrations, the characterization of sensitivity and operational temperatures. Compared to traditional gas sensors, the designed gas microsensors show higher sensitivity to detect CO gas by increasing variation of sensing resistance up to 146.1 % by sensing CO gas concentrations from 40 to 1000 ppm in 200 ℃ and to detect CHCl3 gas by increasing variation of sensing resistance up to 2.99 % by sensing CHCl3 gas concentrations from 10000 to 21000 ppm in room temperature.

碩士
逢甲大學
自動控制工程所
99
A novel CO gas microsensor with tungsten oxide (WO3) sensing film on nanoporous anodic aluminum oxide (AAO) layer has been performed on anodic aluminum oxide template at operation temperature of 25 ℃. Based on microelectromechanical system (MEMS) technology, the microstructures are realized with porous AAO template, WO3 thin films, heaters, and interdigital temperature sensors. The platinum films were deposited to form the heaters, temperature sensors, and interdigital electrodes. To enhance sensitivity, the sputtered WO3 was grown on various nanoporous AAO structures. The study develops a novel porous anodic alumina processing system with a functional current feedback control module that provides control different conditions of voltage, temperature, and etching time to obtain uniform size of AAO film in the range from 20 nm to 104 nm. The self-ordered alumina membranes with a wide range of pore sizes are also achieved to increase sensing area of the microsensor. Experimental results are analyzed to find the relationship between the CO gas concentrations, the characterization of sensitivity and operational temperatures. Compared to traditional gas sensors, the designed CO gas microsensors show higher sensitivity by increasing variation of sensing resistance up to 87.4 % by sensing CO gas concentrations from 100 to 1000 ppm.

博士
國立中興大學
機械工程學系所
103
This study illustrates an integrated gas microsensors array chip fabricated using the standard 0.18 μm CMOS (complementary metal oxide semiconductor) process. The chip includes four gas sensors, four readout circuits and thermometers. The objectives of this study are to utilize the integrated gas microsensors array chip to detect four kinds of volatile organic compound (VOC) gases, the relative humidity of the surroundings and the ambient temperature. After completion of the CMOS process, the chip requires a post-process to etch the sacrificial layer between the interdigitated electrodes and to coat the sensitive film on the electrodes. The sensitive films of integrated gas microsensors array chips are α-Fe2O3, CuO, SnO2, ZrO2 and ZnO, which have good responses for detecting acetone, methanol, ethanol, ammonia and humidity gases, respectively. The characterizations of the sensitive films are observed using a field-emission scanning electron microscope (FE-SEM) to investigate the surface morphology and grain size. Energy dispersive spectrometry (EDS) and x-ray diffraction (XRD) are employed to estimate the chemical component analysis. The experimental results show that the sensitive films synthesized by the hydrothermal method can help the gas microsensors enhance the response due to a high surface-to-volume ratio and high pore density. The gas microsensors array chip has a high response and good selectively for detection of VOC gases. The response of VOC microsensors decreased as the relative humidity of the ambient increased. In the measurement of the gas microsensors integrated with the circuit, the ring oscillator circuit successfully converts the capacitance variation of the microsensors into the oscillation frequency output. The response of the gas microsensors integrated with the circuit is about 0.4-1.1 MHz/ppm. This study further measures the characteristics of the integrated gas microsensors array chip in an environment with multiple VOC gases (acetone, methanol, ethanol and ammonia). Measurement results demonstrate that these VOC microsensors can identify the target gases in multiple gas environments and realizes the objectives of real-time detection.

碩士
逢甲大學
自動控制工程學系
103
The research presents the design of metal-oxide semiconductor gas microsensors based on MEMS technology and nano-properties for sensing CO gas. Sensitivity is defined by measuring the variation of resistance for sensing layers caused by Schottky contanct when gas specimens adsorb on the surface of sensing films. In2O3 nanofibers sensing film with heaters is fabricated by electrospinning, lithography and deep etching processes. The devices can increase effective sensing area for chemical reactions on which CO gas molecules can be adsorbed to improve operation process and response time. Fabrication parameters of indium oxide sensing films are discussed at different voltage, flow rate, collection distance, to perform optimal nanofibers. The sensitivity for sensing the concentration of CO gas is concluded. This sensor integrated the heater temperature sensor and carbon monoxide gas sensor, with characteristic measurements as a result, validation and production of micro gas sensor characteristics are discussed. The heater of the sensor when additional 60 V, the highest temperature can reach 162 ℃, temperature sensor response to linear its sensitivity is 2.09 Ω/℃, gas sensor optimal operating temperature is 160 ℃. Electrostatic spinning wire sensor, measurement of carbon monoxide concentration of 50 to 500 ppm, resistance rate of 1.082 to 1.804.

碩士
逢甲大學
自動控制工程學系
104
A compound sensing structure based on nanoflower-like zinc oxide (ZnO-SnO2) on the top of the nanoporous anodic aluminum oxide (AAO) layer is developed. The powder agglomeration phenomenon of microfabrication process was improved by using a surfactant to obtain uniform nanoflowers of ZnO-SnO2 as a sensing layer for detecting ethanol and methanol gases. The ZnO-SnO2 powders were synthesized using hydrothermal synthesis method. The crystalline phases and purity of the synthesized 3D hierarchical SnO2 nanostructures were analyzed using a X-ray powder diffraction (XRD) that illustrated diffraction patterns accord well with tetragonal rutile SnO2 of the JCPDS Card (no. 41-1445). The uniform nanorods of SnO2 formed unique loose and porous structures increase the accessible surface area of the materials to significantly improve gas diffusion and mass transport. A microheater was designed to control local temperature to promote gas sensitivity. The methanol response of the ZnO-SnO2-AAO structure is high because the porous AAO had improved greatly the specific adsorption surface area, and the ZnO produce more electron donor states or oxygen vacancies to enhance oxygen adsorption as well as the heterojunction of SnO2 and ZnO grains offers access to facile electronic interaction to enhance the surface reaction between adsorbed oxygen and current-carrying electrons. The developed ZnO-SnO2-AAO gas sensing structures include many advantages: simple fabrication process, low cost, high specific surface area, dense porosity, rapid detection, linear sensitivity, high stability, and good repeatability and reproducibility.

碩士
逢甲大學
自動控制工程學系
102
The research presents the design of metal-oxide semiconductor micro gas sensors base on MEMS technology with nano-properties for CO gas sensing. Sensitivity is defined by measuring the variation of resistance for sensing layers caused by Schottky contanct when gas specimens adsorb on the surface of sensing films. Using via lithography to produce patterns on the wafer. Then using the coaxial electrospinning technology to produce indium oxide nano hollow fiber spinning on the wafer as the sensing film, and a heater made via lithography and deep etching processes, in order to increase the effective area and chemical reactions on which gas molecules can be adsorbed. the properties of operation and response time. Experimental Investigation of indium oxide films in different senses the in needle and the outer needle flow rate on nano-fibers, as well as sensitivity to changes in the concentration of carbon monoxide gas. The results showed that indium sensing oxide films at 280 ℃ sensing of CO gas can reach the highest sensitivity. The sensorusesan electrostatic spinning sense of indium oxide nano-fiber sensors for measurement of film,the measuring the carbon monoxide concentration in the range of 50 ~ 1000 ppm, the resistance change rate of 1 to 13.

碩士
逢甲大學
產業研發碩士班
97
This study presents the design of metal-oxide micro gas sensors based on MEMS technology with porous silicon and nano-properties for NOx gas sensing in low concentration(5ppm) at relative low temperature(25℃∼60℃). Sensitivity is defined by measuring the variation of resistance for sensing layers caused by Schottky contact when gas specimens adsorb on the surface of sensing films. It is proposed that sensing films deposited onto the porous silicon surface fabricated by electrochemical etching are mixed with WO3 and MWCNTs by a sol-gel technique in order to increase effective area and chemical reactions on which gas molecules can be adsorbed. Interdigitated Ni catalytic electrodes are deposited onto the sensing films with a shadow mask by evaporating to improve gas adsorption on the surface of sensing films and increasing sensitivity. The gas micro sensor is also integrated with a heater made via lithography and deep etching processes for enhancing the properties of operation and response time. Experiments reveal the highest sensitivity of WO3 films is occured in the 5ppm of NOx at 60℃ and it is possible to detect 5ppm of NOx in room temperature. The response and recovery time of gas micro sensors are decreased with rising temperature that are 25s and 32s at lowest respectively. The results investigate the variation of sensitivities for sensing layers at various operating temperatures and different concentrations of NOx. The influence of dimensions for porous silicon and catalytic electrode on sensing response is also discussed.

Nous proposons dans le cadre de ce travail de thèse, une nouvelle approche de la détection non invasive de l’alcoolémie sanguine à l’aide de microcapteurs d’éthanol à base de SnO2. Cette méthodologie se base sur une détection indirecte de l’alcoolémie sanguine par une mesure des vapeurs d’éthanol émises par la perspiration cutanée suite à une consommation d’alcool. Afin de valider cette approche, il a fallu dans un premier temps démontrer la pertinence et la faisabilité de cette méthodologie de détection par la réalisation d’essais cliniques pilotes en collaboration avec une équipe médicale d’étude pharmacologique du CPCET Marseille. Les différentes mesures du taux d’éthanol réalisées dans les fluides biologiques tels que le sang et l’air expiré ont pu être précisément corrélées avec les mesures de vapeurs d’éthanol réalisées à travers la perspiration à l’aide de trois microcapteurs de gaz commerciaux à base d’oxydes métalliques intégrés à un bracelet. Ces dispositifs ont l’avantage d’être sensibles mais pas sélectifs à la nature du gaz détecté. Durant ces travaux, des couches sensibles de SnO2 ont été déposées par pulvérisation cathodique RF magnétron réactive sur un transducteur breveté par notre équipe, intégrant trois capteurs sur une même puce. L’optimisation des paramètres de dépôt et les analyses structurales des couches de SnO2, nous ont permis de réaliser un multicapteur d’éthanol démontrant des performances sous éthanol ; en termes de sensibilité sous atmosphère humide, de répétabilité et de temps de réponses et de recouvrement ainsi que du point de vue sélectivité
A new approach of a noninvasive detection of blood alcohol concentration using ethanol microsensors based on SnO2 Is developed in this work. The methodology is based on an indirect detection of blood alcohol concentration by measuring the ethanol vapor emitted through the skin perspiration after alcohol consumption. In order to validate this approach, first we demonstrated the relevance and the feasibility of this detection method by carrying out pilot clinical trials in collaboration with a medical team of pharmacological study of CPCET Marseille. The different measurements of the ethanol concentration carried out in biological fluids such as blood and exhaled air could be precisely correlated with the measurements of ethanol vapors performed through the perspiration using three commercial gas microsensors based on metal oxides integrated into a bracelet. . These devices have the advantage of being sensitive but not selective to the nature of the gas detected. During this thesis work, sensitive layers of SnO2 were deposited by reactive magnetron RF sputtering on a transducer patented by our team, integrating three sensors on the same chip. The optimization of the deposition parameters and the structural analyzes of the SnO2 layers, allowed us to develop an ethanol multi-sensor demonstrating performances under ethanol; in terms of sensitivity on humidity, repeatability and response and recovery times as well as from the point of selectivity

碩士
輔仁大學
化學系
95
Monolayer Protected Gold nano-Clusters(MPC) were synthesized by the two phase method and used as organic vapor sensing materials in this research. We have synthesized four different ligand shell protected nano-cluster including 1-Octanethiol, Isooctyl 3-mercapropionate and mixed ligand of 1-Octanethiol: 3-mercaptopropionic acid, 4-pyridinethiol. The four MPC’s materials coated with array of chemiresistor micro- sensors and integrated gas chromatograph detector for 8 organic vapors sensing of various functional groups. We established the model of gas molecules diffuse in to the thin film of MPC. The detector responses are rapid, reversible and highly, selective, due to the unigae shell ligand structure of MPC of different functional group. Limits of detection range from 3 to 100 ng. It is also shown that larger sensor active area resulting higher sensitivity under the same linear flow rate. At different temperature testing, the sensitivities decreased MPC-array sorption of different temperature, and MPC film thickness was between 36 to 72 nm by calculation. According to the diffusion model, we estimated that diffusion coefficients are at the order of ~10-16 m2/sec. The diffusion coefficient value determined the depth of gas diffusion. The correlation coefficient between sensitive and depth are from 0.91 to 0.99. However, the sensitivis vapors are mainly determined by the partition coefficients and the resistance conversion coefficients. The differences among vapor’s diffusion coefficients do not influence the sensitivity trend.