| 1. |
- Svanberg, Sune
(författare)
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Chemical sensing with laser spectroscopy
- 1996
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Ingår i: Sensors and Actuators B: Chemical. - : Elsevier BV. - 0925-4005. ; 33:1-3, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- Laser spectroscopic techniques constitute powerful tools for chemical sensing. Atoms and molecules can be identified and quantified by their specific spectral signatures and the strength of the signals. A wide variety of methods for establishing spectroscopic contact with the species exist: absorption, emission, fluorescence, Raman scattering, acousto-optic, and opto-galvanic phenomena can be employed. Extreme sensitivity and specificity characterise the methods, which can be used for in situ monitoring and in some cases, for remote sensing. Through the special properties of laser radiation it is particularly simple to combine laser spectroscopy with fibre-optical techniques.
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| 2. |
- Jager, Edwin, 1973-, et al.
(författare)
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On-chip microelectrodes for electrochemistry with moveable PPy bilayer actuators as working electrodes
- 1999
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Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 56:1-2, s. 73-78
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Tidskriftsartikel (refereegranskat)abstract
- We present electrochemical microactuators which have all the electrodes necessary for the actuation—the working, counter, and reference electrodes—on-chip. This is a first step towards an all-polymer system, i.e., a system that does not require a liquid electrolyte. The microactuators' performance was as good as when standard, off-chip counter and reference electrodes were used. Specifically, the speed of actuation was the same. In addition, we obtained a good cyclic voltammogram, although the oxidation and reduction peaks were shifted and some noise was present. Apart from application in an all-polymer system, we will also use these microactuators for studies on the effect of mechanical stimulation of living cells.
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| 3. |
- Baranzahi, Amir, et al.
(författare)
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Gas sensitive field effect devices for high temperature
- 1995
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 26:1-3, s. 165-169
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Tidskriftsartikel (refereegranskat)abstract
- Field effect sensors based on metal-oxide-silicon carbide (MOSiC) devices are used as high temperature gas sensors. They are sensitive to, for example, saturated hydrocarbons and hydrogen and can be operated up to at least 800 degrees C, which make them suitable for several types of combustion control. A metal gate with two layer platinum and a buffer layer of tantalum silicide in between gave a large increase in the long term stability of the sensors. At temperatures below 600 degrees C, the response to ethane in oxygen was shown to have a threshold at a ratio of about 0.38 for the ethane-to-oxygen concentrations. Below this ratio, the surface can be considered as mainly oxygen covered and the response is small. Above this ratio the metal surface is probably mainly hydrogen covered and the response is considerably larger.
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| 4. |
- Baranzahi, Amir, et al.
(författare)
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Response of metal-oxide-silicon carbide sensors to simulated and real exhaust gases
- 1997
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 43:1-3, s. 52-59
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Tidskriftsartikel (refereegranskat)abstract
- Field effect devices based on catalytic metal-oxide-silicon carbide (MOSiC) structures can be used as high temperature gas sensors. The devices are sensitive to hydrocarbons and hydrogen and can be operated up to at least 900 degrees C, which make them suitable for several combustion applications, Simulated and real exhaust gases from a car engine have been studied at sensor temperatures from 200 to 650 degrees C, and it was round that the sensor signal is high for excess hydrocarbon and low for excess oxygen. The response time is less than 100 ms and only a small degradation of the devices was observed after several days of operation. The devices also react to changes of the gas composition In the fuel-rich and fuel-lean region. The devices show an interesting temperature dependence in the fuel rich region.
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| 5. |
- Eriksson, Mats, 1963-, et al.
(författare)
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The influence of CO on the response of hydrogen sensitive Pd-MOS devices
- 1997
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Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 42:3, s. 217-223
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Tidskriftsartikel (refereegranskat)abstract
- In order to understand and correctly interpret the response of chemical sensors under measurement conditions, detailed studies of molecule—sensor interactions under well-controlled conditions are needed. In this work, the influence of CO on the response of a hydrogen sensitive Pd—metal-oxide-semiconductor (Pd—MOS) device with a dense Pd film is studied in ultrahigh vacuum (UHV). The results show that although CO by itself does not induce any response of the device, CO may have a significant influence on the hydrogen response, especially so in the presence of oxygen. It is also shown that high CO coverages on the Pd surface increases the time needed to obtain equilibrium between the gas phase hydrogen pressure and the response of the Pd—MOS device. This is due to a CO induced increase of the activation energies of the dissociation and association processes for hydrogen. The effect on the hydrogen response is small for CO coverages below 0.2 monolayers and increases dramatically above this coverage.
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| 6. |
- Heideman, René, et al.
(författare)
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Fabrication and packaging of integrated chemo-optical sensors
- 1996
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Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 35:1-3, s. 234-240
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the design and fabrication of a sensitive integrated chemo-optical sensor supplied with on-chip fiber-to-waveguide connectors. The sensor is designed for TE-polarized light with wavelength of 633 nm. The fiber-to-chip connectors are based on easily fabricated silicon V-grooves combined with a smooth sawcut. The sawcut is defining the channel waveguide endface. The sensor is based on a phase modulated Mach-Zehnder interferometer, using the electro-optic effect of the waveguiding material zinc oxide (ZnO). The fiber-to-chip connector units have a typical coupling efficiency of 0.1–1%. The electro-optical voltage × length product Vπ is 15 ± 4 V cm at frequencies above 100 Hz. Preliminary experiments on the general (passive) sensor response showing its expected high sensitivity are discussed.
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| 7. |
- Lundström, Ingemar, et al.
(författare)
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Recent developments in field-effect gas sensors
- 1995
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 23:2-3, s. 127-133
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Tidskriftsartikel (refereegranskat)abstract
- Some of the ongoing studies at our laboratory of gas-sensitive field-effect devices with catalytic metal gates are reviewed. More particularly, we discuss the use of such devices in so-called electronic noses due to the possibility of changing the selectivity patterns of the devices by the choice of catalytic metal and operation temperature. Several examples of the application of electronic noses consisting of field-effect devices in combination with metal oxide-based sensors are given. Finally, a summary is given of some remaining scientific problems and studies related to the understanding and development of gas-sensitive field-effect devices.
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| 8. |
- Nakagomi, Shinji, et al.
(författare)
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Influence of carbon monoxide, water and oxygen on high temperature catalytic metal-oxide-silicon carbide structures
- 1997
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 45:3, s. 183-191
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Tidskriftsartikel (refereegranskat)abstract
- High temperature sensors, Schottky diodes and capacitors, based on catalytic metal-oxide-silicon carbide devices are investigated. Reducing gases like hydrogen and other hydrogen containing gases, decrease the barrier height and the flat band voltage, respectively, which is used as the sensor signal. The sensitivity of the devices at 600 degrees C to mixtures of carbon monoxide and oxygen with and without water vapour is studied in this paper. A large binary response of the sensors to carbon monoxide similar to the sensor response to hydrogen gas is observed. Close to the stoichiometric ratio of carbon monoxide and oxygen, the signal changes from a high to a low value corresponding to an excess of carbon monoxide and an excess of oxygen, respectively. When hydrogen is added to a mixture of carbon monoxide and oxygen, the signal changes from a high to a low value at a higher oxygen concentration. Since the response of these devices to hydrogen and hydrogen containing gases is supposed to emanate from hydrogen atoms, the mechanism of the response to carbon monoxide is discussed. The signal to carbon monoxide as well as to hydrogen decreases in the presence of water vapour and the reason for this is discussed.
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| 9. |
- Svenningstorp, Henrik, et al.
(författare)
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Influence of catalytic reactivity on the response of metal-oxide-silicon carbide sensor to exhaust gases
- 1999
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 57:1-3, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic metal insulator silicon carbide, MISiC, Schottky diodes are promising devices for on board exhaust diagnosis in cars. These sensors show a direct or indirect sensitivity to gases like H-2, CO, HC (hydrocarbons) and O-2. The catalytic reactivity of the sensor will effect the gas sensing conditions. In some situations knowledge about the reactivity of the catalytic surface may give more information about the exhaust gas composition. For instance, the sensor signal normally moves to a lower voltage in an ambient containing H-2 and HC, however, under certain conditions when exposed to rich gas mixtures, the HC response is opposite the one for H-2. Measurements performed by the MISiC sensors on simulated exhaust gas mixtures, either rich or lean, are shown here. Some fundamental studies of the HC response have been performed. Reaction limitation conditions are suggested as an explanation for the response of HC opposite the one of H-2.
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| 10. |
- Tobias, Peter, et al.
(författare)
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Moving gas outlets for the evaluation of fast gas sensors
- 1999
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 58:1-3, s. 389-393
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Tidskriftsartikel (refereegranskat)abstract
- A new method for the evaluation of fast gas sensors is described. By using moving gas outlets, we can quickly change the ambient around a sensor. Different platinum-insulator-silicon carbide (MISiC) structures are investigated. Their sensor response contains fast components, which respond within milliseconds to a change in the ambient from a reducing gas to an oxidising gas and vice versa. Cylinder specific monitoring of car engines with the MISiC structures is discussed.
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