| 1. |
- Andersson, Mike, et al.
(author)
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SiC-FET sensors for selective and quantitative detection of VOCs down to ppb level
- 2016
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In: Procedia Engineering. - : Elsevier. - 1877-7058. ; 168, s. 216-220
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Journal article (peer-reviewed)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.
(author)
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Low-cost chemical gas sensors for selective formaldehyde quantification at ppb-level in field tests
- 2017
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Conference paper (peer-reviewed)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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| 3. |
- Bastuck, Manuel, et al.
(author)
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UV-assisted gate bias cycling in gas-sensitive field-effect transistors
- 2018
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In: Proceedings. - Basel Switzerland : MDPI. - 2504-3900. ; 2:13
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Journal article (peer-reviewed)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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| 4. |
- Bur, Christian, et al.
(author)
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Discrimination and Quantification of Volatile Organic Compounds in the ppb-Range with Gas Sensitive SiC-FETs Using Multivariate Statistics
- 2015
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In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 214, s. 225-233
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Journal article (peer-reviewed)abstract
- Gas sensitive field effect transistors based on silicon carbide, SiC-FETs, have been studied for indoor air quality applications. The selectivity of the sensors was increased by temperature cycled operation, TCO, and data evaluation based on multivariate statistics. Discrimination of benzene, naphthalene, and formaldehyde independent of the level of background humidity is possible by using shape describing features as input for Linear Discriminant Analysis, LDA, or Partial Least Squares – Discriminant Analysis, PLS-DA. Leave-one-out cross-validation leads to a correct classification rate of 90 % for LDA, and for PLS-DA a classification rate of 83 % is achieved. Quantification of naphthalene in the relevant concentration range, i.e. 0 ppb to 40 ppb, was performed by Partial Least Squares Regression and a combination of LDA with a second order polynomial fit function. The resolution of the model based on a calibration with three concentrations was approximately 8 ppb at 40 ppb naphthalene for both algorithms.Hence, the suggested strategy is suitable for on demand ventilation control in indoor air quality application systems.
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| 5. |
- Bur, Christian, et al.
(author)
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Discrimination and Quantification of Volatile Organic Compounds in the ppb-Range with Gas Sensitive SiC-Field Effect Transistors
- 2014
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In: Procedia Engineering. - : Elsevier. - 1877-7058.
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Conference paper (peer-reviewed)abstract
- Gas sensitive FETs based on SiC have been studied for the discrimination and quantification of hazardous volatile organiccompounds (VOCs) in the low ppb range. The sensor performance was increased by temperature cycled operation (TCO) anddata evaluation based on multivariate statistics, here Linear Discriminant Analysis (LDA). Discrimination of formaldehyde,naphthalene and benzene with varying concentrations in the ppb range is demonstrated. In addition, it is shown that naphthalenecan be quantified in the relevant concentration range independent of the relative humidity and against a high ethanol background.Hence, gas sensitive SiC-FETs are suitable sensors for determining indoor air quality.
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| 6. |
- Bur, Christian, et al.
(author)
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Increasing the Selectivity of Pt-Gate SiC Field Effect Gas Sensors by Dynamic Temperature Modulation
- 2012
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In: IEEE Sensors Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1530-437X .- 1558-1748. ; 12:6
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Journal article (peer-reviewed)abstract
- Based on a diode coupled silicon carbide field effect transistor (FET) with platinum as catalytic gate material, the influence of dynamic temperature modulation on the selectivity of gas analysis sensors FETs has been investigated. This operating mode, studied intensively for semiconductor gas sensors, has only recently been applied to FETs. A suitable temperature cycle for detection of typical exhaust gases (CO, NO, C3H6, H-2, NH3) was developed and combined with appropriate signal processing. The sensor data were evaluated using multivariate statistics, e.g., linear discriminant analysis. Measurements have proven that typical exhaust gases can be discriminated in backgrounds with 0, 10, and 20% oxygen. Furthermore, we are able to quantify the mentioned gases and to determine unknown concentrations based on training data. Very low levels of relative humidity below a few percent influence the sensor response considerably but for higher levels the cross interference of humidity is negligible. In addition, experiments regarding stability and reproducibility were performed.
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| 7. |
- Bur, Christian, et al.
(author)
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New method for selectivity enhancement of SiC field effect gas sensors for quantification of NO (x)
- 2012
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In: Microsystem Technologies. - : Springer Verlag (Germany). - 0946-7076 .- 1432-1858. ; 18:7-8, s. 1015-1025
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Journal article (peer-reviewed)abstract
- A silicon carbide based enhancement type metal insulator field effect transistor with porous gate metallization has been investigated as a total NO (x) sensor operated in a temperature cycling mode. This operating mode is quite new for gas sensors based on the field effect but promising results have been reported earlier. Based on static investigations we have developed a suitable T-cycle optimized for NO (x) detection and quantification in a mixture of typical exhaust gases (CO, C2H4, and NH3). Significant features describing the shape of the sensor response have been extracted and evaluated with multivariate statistics (e.g. linear discriminant analysis) allowing quantification of NO (x) . Additional cleaning-cycles every 30 min improve the stability of the sensor further. With this kind of advanced signal processing the influence of sensor drift and cross sensitivity to ambient gases can be reduced effectively. Measurements have proven that different concentrations of NO (x) can be detected even in a changing mixture of other typical exhaust gases under dry and humid conditions. In addition to that, unknown concentrations of NO (x) can be detected based on a small set of training data. It can be concluded that the performance of GasFETs for NO (x) determination can be enhanced considerably with temperature cycling and appropriate signal processing.
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| 8. |
- Bur, Christian, et al.
(author)
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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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In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 193, s. 931-940
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Journal article (peer-reviewed)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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| 9. |
- Laj, Paolo, et al.
(author)
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A global analysis of climate-relevant aerosol properties retrieved from the network of Global Atmosphere Watch (GAW) near-surface observatories
- 2020
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In: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 13:8, s. 4353-4392
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Journal article (peer-reviewed)abstract
- Aerosol particles are essential constituents of the Earth's atmosphere, impacting the earth radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. In contrast to most greenhouse gases, aerosol particles have short atmospheric residence times, resulting in a highly heterogeneous distribution in space and time. There is a clear need to document this variability at regional scale through observations involving, in particular, the in situ near-surface segment of the atmospheric observation system. This paper will provide the widest effort so far to document variability of climate-relevant in situ aerosol properties (namely wavelength dependent particle light scattering and absorption coefficients, particle number concentration and particle number size distribution) from all sites connected to the Global Atmosphere Watch network. High-quality data from almost 90 stations worldwide have been collected and controlled for quality and are reported for a reference year in 2017, providing a very extended and robust view of the variability of these variables worldwide. The range of variability observed worldwide for light scattering and absorption coefficients, single-scattering albedo, and particle number concentration are presented together with preliminary information on their long-term trends and comparison with model simulation for the different stations. The scope of the present paper is also to provide the necessary suite of information, including data provision procedures, quality control and analysis, data policy, and usage of the ground-based aerosol measurement network. It delivers to users of the World Data Centre on Aerosol, the required confidence in data products in the form of a fully characterized value chain, including uncertainty estimation and requirements for contributing to the global climate monitoring system.
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| 10. |
- Michaud, Dominique S., et al.
(author)
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Reproductive Factors and Exogenous Hormone Use in Relation to Risk of Glioma and Meningioma in a Large European Cohort Study
- 2010
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In: Cancer Epidemiology Biomarkers & Prevention. - 1538-7755 .- 1055-9965. ; 19:10, s. 2562-2569
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Journal article (peer-reviewed)abstract
- Background: The etiologies of glioma and meningioma tumors are largely unknown. Although reproductive hormones are thought to influence the risk of these tumors, epidemiologic data are not supportive of this hypothesis; however, few cohort studies have published on this topic. We examined the relation between reproductive factors and the risk of glioma and meningioma among women in the European Prospective Investigation into Cancer and Nutrition (EPIC). Methods: After a mean of 8.4 years of follow-up, 193 glioma and 194 meningioma cases were identified among 276,212 women. Information on reproductive factors and hormone use was collected at baseline. Cox proportional hazard regression was used to determine hazard ratios (HR) and 95% confidence intervals (95% CI). Results: No associations were observed between glioma or meningioma risk and reproductive factors, including age at menarche, parity, age at first birth, menopausal status, and age at menopause. A higher risk of meningioma was observed among postmenopausal women who were current users of hormone replacement therapy (HR, 1.79; 95% CI, 1.18-2.71) compared with never users. Similarly, current users of oral contraceptives were at higher risk of meningioma than never users (HR, 3.61; 95% CI, 1.75-7.46). Conclusion: Our results do not support a role for estrogens and glioma risk. Use of exogenous hormones, especially current use, seems to increase meningioma risk. However, these findings could be due to diagnostic bias and require confirmation. Impact: Elucidating the role of hormones in brain tumor development has important implications and needs to be further examined using biological measurements. Cancer Epidemiol Biomarkers Prev; 19(10); 2562-9. (C) 2010 AACR.
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| 11. |
- Puglisi, Donatella, et al.
(author)
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Catalytic metal-gate field effect transistors based on SiC for indoor air quality control
- 2015
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In: Journal of Sensors and Sensor Systems. - Germany : Copernicus. - 2194-8771 .- 2194-878X. ; 4, s. 1-8
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Journal article (peer-reviewed)abstract
- High-temperature iridium-gated field effect transistors based on silicon carbide have been used for sensitive detection of specific volatile organic compounds (VOCs) in concentrations of health concern, for indoorair quality monitoring and control. Formaldehyde, naphthalene, and benzene were studied as hazardous VOCs at parts per billion (ppb) down to sub-ppb levels. The sensor performance and characteristics were investigated at a constant temperature of 330° C and at different levels of relative humidity up to 60 %, showing good stability and repeatability of the sensor response, and excellent detection limits in the sub-ppb range.
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| 12. |
- Puglisi, Donatella, et al.
(author)
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Exploring the gas sensing performance of catalytic metal/ metal oxide 4H-SiC field effect transistors
- 2016
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In: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 858, s. 997-1000
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Journal article (peer-reviewed)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.
(author)
-
Mastering VOC detection for better indoor air quality
- 2014
-
Conference paper (peer-reviewed)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. |
- Puglisi, Donatella, et al.
(author)
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Silicon carbide field effect transistors for detection of ultra-low concentrations of hazardous volatile organic compounds
- 2014
-
In: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 778-780, s. 1067-1070
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Journal article (peer-reviewed)abstract
- Gas sensitive silicon carbide field effect transistors with nanostructured Ir gate layershave been used for the first time for sensitive detection of volatile organic compounds (VOCs) atpart per billion level, for indoor air quality applications. Formaldehyde, naphthalene, and benzenehave been used as typical VOCs in dry air and under 10% and 20% relative humidity. A singleVOC was used at a time to study long-term stability, repeatability, temperature dependence, effectof relative humidity, sensitivity, response and recovery times of the sensors.
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| 15. |
- Rodner, Marius, et al.
(author)
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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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In: JOURNAL OF SENSORS AND SENSOR SYSTEMS. - : COPERNICUS GESELLSCHAFT MBH. - 2194-8771 .- 2194-878X. ; 8:2, s. 261-267
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Journal article (peer-reviewed)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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| 16. |
- Rodner, Marius, 1991-, et al.
(author)
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Iron oxide nanoparticle decorated graphene for ultra-sensitive detection of volatile organic compounds
- 2018
-
In: Proceedings. - Basel Switzerland : MDPI. - 2504-3900. ; 2:13
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Journal article (peer-reviewed)abstract
- It has been found that two-dimensional materials, such as graphene, can be used as remarkable gas detection platforms as even minimal chemical interactions can lead to distinct changes in electrical conductivity. In this work, epitaxially grown graphene was decorated with iron oxide nanoparticles for sensor performance tuning. This hybrid surface was used as a sensing layer to detect formaldehyde and benzene at concentrations of relevance in air quality monitoring (low parts per billion). Moreover, the time constants could be drastically reduced using a derivative sensor signal readout, allowing detection at the sampling rates desired for air quality monitoring applications.
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| 17. |
- Rodner, Marius, et al.
(author)
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Metal Oxide Nanolayer-Decorated Epitaxial Graphene : A Gas Sensor Study
- 2020
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In: Nanomaterials. - : MDPI. - 2079-4991. ; 10:11
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Journal article (peer-reviewed)abstract
- In this manuscript, we explore the sensor properties of epitaxially grown graphene on silicon carbide decorated with nanolayers of CuO, Fe3O4, V2O5, or ZrO2. The sensor devices were investigated in regard to their response towards NH3 as a typical reducing gas and CO, C6H6, CH2O, and NO2 as gases of interest for air quality monitoring. Moreover, the impact of operating temperature, relative humidity, and additional UV irradiation as changes in the sensing environment have been explored towards their impact on sensing properties. Finally, a cross-laboratory study is presented, supporting stable sensor responses, and the final data is merged into a simplified sensor array. This study shows that sensors can be tailored not only by using different materials but also by applying different working conditions, according to the requirements of certain applications. Lastly, a combination of several different sensors into a sensor array leads to a well-performing sensor system that, with further development, could be suitable for several applications where there is no solution on the market today.
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