| 1. |
- Andersson, Mike, et al.
(författare)
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SiC-FET sensors for selective and quantitative detection of VOCs down to ppb level
- 2016
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Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 168, s. 216-220
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Tidskriftsartikel (refereegranskat)abstract
- With the increased interest in development of cheap, simple means for indoor air quality monitoring, and specifically in relation to certain well-known pollutant substances with adverse health effects even at very low concentrations, such as different Volatile Organic Compounds (VOCs), this contribution aims at providing an overview of the development status of the silicon carbide field effect transistor (SiC FET) based sensor platform for ppb level detection of VOCs. Optimizing the transducer design, the gas-sensitive material(s) composition, structure and processing, its mode of operation - applying temperature cycled operation in conjunction with multivariate data evaluation - and long-term performance it has been possible to demonstrate promising resultsregarding the sensor technology’s ability to achieve both single-digit ppb sensitivity towards e.g. naphthalene as well as selective detection of individual substances in a mixture of different VOCs.
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| 2. |
- Bastuck, Manuel, et al.
(författare)
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Characterizing the Influence of Gate Bias on Electrical and Catalytical Properties of a Porous Platinum Gate on Field Effect Gas Sensors
- 2016
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Ingår i: 2016 IEEE SENSORS. - : IEEE. - 9781479982875
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Konferensbidrag (refereegranskat)abstract
- In this work, we exposed an MIS capacitor with porous platinum as gate material to different concentrations of CO and NH3. Its capacitance and typical reaction products (water, CO2 and NO) were monitored at high and low oxygen concentration and different gate bias voltages. We found that the gate bias influences the switch-point of the binary CO response usually seen when either changing the temperature at constant gas concentrations or the CO/O-2 ratio at constant temperature. For NH3, the sensor response as well as product reaction rates increase with bias voltages up to 6 V. A capacitance overshoot is observed when switching on or off either gas at low gate bias, suggesting increasing oxygen surface coverage with decreasing gate bias.
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| 3. |
- Bastuck, Manuel, et al.
(författare)
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Comparison of ppb-level gas measurements with a metal-oxide semiconductor gas sensor in two independent laboratories
- 2018
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Ingår i: Sensors and actuators. B, Chemical. - : ELSEVIER SCIENCE SA. - 0925-4005 .- 1873-3077. ; 273, s. 1037-1046
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we use a gas sensor system consisting of a commercially available gas sensor in temperature cycled operation. It is trained with an extensive gas profile for detection and quantification of hazardous volatile organic compounds (VOC) in the ppb range independent of a varying background of other, less harmful VOCs and inorganic interfering gases like humidity or hydrogen. This training was then validated using a different gas mixture generation apparatus at an independent lab providing analytical methods as reference. While the varying background impedes selective detection of benzene and naphthalene at the low concentrations supplied, both formaldehyde and total VOC can well be quantified, after calibration transfer, by models trained with data from one system and evaluated with data from the other system. The lowest achievable root mean squared errors of prediction were 49 ppb for formaldehyde (in a concentration range of 20-200 ppb) and 150 mu g/m(3) (in a concentration range of 25-450 mu g/m(3)) for total VOC. The latter uncertainty improves to 13 mu g/m(3) with a more confined model range of 220-320 mu g/m(3). The data from the second lab indicate an interfering gas which cannot be detected analytically but strongly influences the sensor signal. This demonstrates the need to take into account all sensor relevant gases, like, e.g., hydrogen and carbon monoxide, in analytical reference measurements.
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| 4. |
- Bastuck, Manuel, et al.
(författare)
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Dynamic multi-sensor operation and read-out for highly selective gas sensor systems
- 2016
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Ingår i: PROCEEDINGS OF THE 30TH ANNIVERSARY EUROSENSORS CONFERENCE - EUROSENSORS 2016. - : ELSEVIER SCIENCE BV. ; , s. 1685-1688
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Konferensbidrag (refereegranskat)abstract
- We describe hardware and algorithms which enable highly selective and sensitive operation of the two gas sensor types used in the SENSIndoor project. The resistance of a metal-oxide semiconductor (MOS) type can rise above 1 G Omega in temperature cycled operation (TCO), which is measured using a logarithmic amplifier. A silicon-carbide based, gas-sensitive field-effect transistor (SiC-FET) driven with a combination of TCO and gate-bias cycled operation (GBCO) is used as second, complimentary sensor. The cyclic sensor signals exhibit distinct shape changes depending on the gas present which is captured by pattern recognition. In this study we use Linear Discriminant Analysis (LDA) for discrimination and Partial Least Squares Regression (PLSR) for quantification of ppb concentrations of target VOCs in changing ppm concentrations of interfering gases for indoor air quality assessment. (C) 2016 The Authors. Published by Elsevier Ltd.
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| 5. |
- Bastuck, Manuel, et al.
(författare)
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Exploring the selectivity of WO3 with iridium catalyst in an ethanol/naphthalene mixture using multivariate statistics
- 2016
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Ingår i: Thin Solid Films. - : ELSEVIER SCIENCE SA. - 0040-6090 .- 1879-2731. ; 618, s. 263-270
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Tidskriftsartikel (refereegranskat)abstract
- Temperature cycled operation and multivariate statistics have been used to compare the selectivity of two gate (i.e. sensitive) materials for gas-sensitive, silicon carbide based field effect transistors towards naphthalene and ethanol in different mixtures of the two substances. Both gates have a silicon dioxide (SiO2) insulation layer and a porous iridium (Ir) electrode. One of it has also a dense tungsten trioxide (WO3) interlayer between Ir and SiO2. Both static and transient characteristics play an important role and can contribute to improve the sensitivity and selectivity of the gas sensor. The Ir/SiO2 is strongly influenced by changes in ethanol concentration, and is, thus, able to quantify ethanol in a range between 0 and 5 ppm with a precision of 500 ppb, independently of the naphthalene concentrations applied in this investigation. On the other hand, this sensitivity to ethanol reduces its selectivity towards naphthalene, whereas Ir/WO3/SiO2 shows an almost binary response to ethanol. Hence, the latter has a better selectivity towards naphthalene and can quantify legally relevant concentrations down to 5 ppb with a precision of 2.5 ppb, independently of a changing ethanol background between 0 and 5 ppm. (C) 2016 Elsevier B.V. All rights reserved.
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| 6. |
- Bastuck, Manuel, et al.
(författare)
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Fusing Cyclic Sensor Data with Different Cycle Length
- 2016
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Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON MULTISENSOR FUSION AND INTEGRATION FOR INTELLIGENT SYSTEMS (MFI). - : IEEE. - 9781467397094 - 9781467397087 ; , s. 72-77
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Konferensbidrag (refereegranskat)abstract
- Cyclic modulation of sensor parameters can improve sensitivity and selectivity of gas sensors. If the modulated parameter influences the sens environment, several readings can be gained, eventually resulting in a multi-dimensional response which can be analyzed with, e.g., principal component analysis. In certain cases, e.g. temperature modulated gas sensors with different thermal time constants, the length of the used cycles, and, thus, the temporal resolution of the sensors can differ. As a consequence, different sensors can produce datasets with an unequal number of observations which, nevertheless, cover the same interval of time. In this work, we explore three different strategies which enable combination of those datasets in order to retain the maximum amount of information from two sensors when used in parallel. Simulated data show that simple combination of a short cycle with the last complete long cycle can improve correct classification rate by 15 percent points while maintaining the better temporal resolution. On the other hand, performance can be further increased at the expense of temporal resolution by adding either several of the short cycles, or their mean, to a long cycle, effectively reducing noise. The proposed combination strategies and their dependence on preprocessing are validated with a real dataset of two gas sensors. Overall, and taking into account differences in data performance for simulated and real data is observed.
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| 7. |
- Bastuck, Manuel, 1990-
(författare)
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Improving the Performance of Gas Sensor Systems with Advanced Data Evaluation, Operation, and Calibration Methods
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to facilitate the widespread use of gas sensors, some challenges must still be overcome. Many of those are related to the reliable quantification of ultra-low concentrations of specific compounds in a background of other gases. This thesis focuses on three important items in the measurement chain: sensor material and operating modes, evaluation of the resulting data, and test gas generation for efficient sensor calibration.New operating modes and materials for gas-sensitive field-effect transistors have been investigated. Tungsten trioxide as gate oxide can improve the selectivity to hazardous volatile organic compounds like naphthalene even in a strong and variable ethanol background. The influence of gate bias and ultraviolet light has been studied with respect to the transport of oxygen anions on the sensor surface and was used to improve classification and quantification of different gases.DAV3E, an internationally recognized MATLAB-based toolbox for the evaluation of cyclic sensor data, has been developed and published as opensource. It provides a user-friendly graphical interface and specially tailored algorithms from multivariate statistics.The laboratory tests conducted during this project have been extended with an interlaboratory study and a field test, both yielding valuable insights for future, more complex sensor calibration. A novel, efficient calibration approach has been proposed and evaluated with ten different gas sensor systems.
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| 8. |
- Bastuck, Manuel, et al.
(författare)
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Low-cost chemical gas sensors for selective formaldehyde quantification at ppb-level in field tests
- 2017
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Konferensbidrag (refereegranskat)abstract
- Data from a silicon carbide based field-effect transistor were recorded over a period of nine days in a ventilated school room. For enhanced sensitivity and selectivity especially to formaldehyde, porous iridium on pulsed laser deposited tungsten trioxide was used as sensitive layer, in combination with temperature cycled operation and subsequent multivariate data processing techniques. The sensor signal was compared to reference measurements for formaldehyde concentration, CO2 concentration, temperature, and relative humidity. The results show a distinct pattern for the reference formaldehyde concentration, arising from the day/night cycle. Taking this into account, the projections of both principal component analysis and partial least squares regression lead to almost the same result concerning correlation to the reference. The sensor shows cross-sensitivity to an unidentified component of human activity, presumably breath, and, possibly, to other compounds appearing together with formaldehyde in indoor air. Nevertheless, the sensor is able to detect and partially quantify formaldehyde below 40 ppb with a correlation to the reference of 0.48 and negligible interference from ambient temperature or relative humidity.
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| 9. |
- Bastuck, Manuel, et al.
(författare)
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UV-assisted gate bias cycling in gas-sensitive field-effect transistors
- 2018
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Ingår i: Proceedings. - Basel Switzerland : MDPI. - 2504-3900. ; 2:13
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Tidskriftsartikel (refereegranskat)abstract
- Static and dynamic responses of a silicon carbide field-effect transistor gas sensor have been investigated at two different gate biases in several test gases. Especially the dynamic effects are gas dependent and can be used for gas identification. The addition of ultraviolet light reduces internal electrical relaxation effects, but also introduces new, temperature-dependent effects.
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| 10. |
- Bur, Christian, et al.
(författare)
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Influence of a Changing Gate Bias on the Sensing Properties of SiC Field Effect Gas Sensors
- 2012
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Ingår i: IMCS 2012. - 9783981348422 ; , s. 140-143
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Field effect transistors based on silicon carbide have previously been used with temperature cycled operation to enhance the selectivity. In this study the influence of a changing gate bias on the sensing properties of a platinum gate FET has been studied in order to extend the virtual multi-sensor approach. The sensor exhibits gas specific hysteresis when changing the gate bias indicating that additional information regarding selectivity is contained in the transient behavior. Measurements also showed that especially the shape of the sensor signal changes dramatically with different gas exposures (e.g. H2, CO or NH3) during relaxation after step changes of the gate bias. The changing shape primarily reflects the gas itself and not the concentration so that the selectivity of the sensor is increased.
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| 11. |
- Bur, Christian, et al.
(författare)
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Selectivity enhancement of SiC-FET gas sensors by combining temperature and gate bias cycled operation using multivariate statistics
- 2014
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 193, s. 931-940
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Tidskriftsartikel (refereegranskat)abstract
- In this paper temperature modulation and gate bias modulation of a gas sensitive field effect transistor based on silicon carbide (SiC-FET) are combined in order to increase the selectivity. Data evaluation based on extracted features describing the shape of the sensor response was performed using multivariate statistics, here by Linear Discriminant Analysis (LDA). It was found that both temperature cycling and gate bias cycling are suitable for quantification of different concentrations of carbon monoxide. However, combination of both approaches enhances the stability of the quantification, respectively the discrimination of the groups in the LDA scatterplot. Feature selection based on the stepwise LDA algorithm as well as selection based on the loadings plot has shown that features both from the temperature cycle and from the bias cycle are equally important for the identification of carbon monoxide, nitrogen dioxide and ammonia. In addition, the presented method allows discrimination of these gases independent of the gas concentration. Hence, the selectivity of the FET is enhanced considerably.
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| 12. |
- Puglisi, Donatella, et al.
(författare)
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Exploring the gas sensing performance of catalytic metal/ metal oxide 4H-SiC field effect transistors
- 2016
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 858, s. 997-1000
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Tidskriftsartikel (refereegranskat)abstract
- Gas sensitive metal/metal-oxide field effect transistors based on silicon carbide were used to study the sensor response to benzene (C6H6) at the low parts per billion (ppb) concentration range. A combination of iridium and tungsten trioxide was used to develop the sensing layer. Highsensitivity to 10 ppb C6H6 was demonstrated during several repeated measurements at a constant temperature from 180 to 300 °C. The sensor performance was studied also as a function of the electrical operating point of the device, i.e., linear, onset of saturation, and saturation mode. Measurements performed in saturation mode gave a sensor response up to 52 % higher than those performed in linear mode.
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| 13. |
- Puglisi, Donatella, et al.
(författare)
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Mastering VOC detection for better indoor air quality
- 2014
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Konferensbidrag (refereegranskat)abstract
- In this study, we use two different sensor technologies based on gas sensitive silicon carbide field effect transistors (SiC-FETs) and epitaxial graphene on SiC (EG/SiC) for highly sensitive and selective detection of trace amounts of three hazardous volatile organic compounds (VOCs), i.e. formaldehyde (CH2O), benzene (C6H6), and naphthalene (C10H8), present in indoor environments in concentrations of health concern.Iridium and platinum are used as sensing layers for the gate contacts. The FET sensors are operated at high temperature, under static and dynamic conditions. Excellent detection limits of 10 ppb for CH2O, about 1 ppb for C6H6, and below 0.5 ppb for C10H8 are measured at 60 % relative humidity (r.h.) [1]. The selectivity of the sensors is increased by temperature cycled operation and data evaluation based on multivariate statistics. Discrimination of CH2O, C6H6, and C10H8 independent of the level of background humidity is possible with a very high cross-validation rate up to 90 % [2]. These results are very encouraging for indoor air quality control, being below the threshold limits recommended by the WHO guidelines.Graphene-based chemical sensors offer the advantage of extreme sensitivity due to graphene’s unique electronic properties and the fact that every single atom is at the surface and available to interact with gas molecules. For this reason, uniform monolayer graphene is crucial [3], which is guaranteed by our optimized epitaxial growth process. Graphene-based chemical gas sensors normally show ultra-high sensitivity to certain gas molecules but suffer from poor selectivity. Functionalization or modification of the graphene surface can improve selectivity, but most such measures result in poor reproducibility. We demonstrate reproducible, non-destructive means of graphene surface decoration with nanostructured metals and metal oxides, and study their effect on the gas interactions at the graphene surface.
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| 14. |
- Rodner, Marius, et al.
(författare)
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Enabling a new method of dynamic field-effect gas sensor operation through lithium-doped tungsten oxide
- 2019
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Ingår i: JOURNAL OF SENSORS AND SENSOR SYSTEMS. - : COPERNICUS GESELLSCHAFT MBH. - 2194-8771 .- 2194-878X. ; 8:2, s. 261-267
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Tidskriftsartikel (refereegranskat)abstract
- To fulfil todays requirements, gas sensors have to become more and more sensitive and selective. Temperature-cycled operation has long been used to enhance the sensitivity and selectivity of metal-oxide semiconductor gas sensors and, more recently, silicon-carbide-based, gas-sensitive field-effect transistors (SiC-FETs). In this work, we present a novel method to significantly enhance the effect of gate bias on a SiC-FETs response, giving rise to new possibilities for static and transient signal generation and, thus, increased sensitivity and selectivity. A tungsten trioxide (WO3) layer is deposited via pulsed laser deposition as an oxide layer beneath a porous iridium gate, and is doped with 0.1 AT% of lithium cations. Tests with ammonia as a well-characterized model gas show a relaxation effect with a time constant between 20 and 30 s after a gate bias step as well as significantly increased response and sensitivity at +/- 2V compared to 0V. We propose an electric field-mediated change in oxygen surface coverage as the cause of this novel effect.
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