| 1. |
- Lloyd Spetz, Anita, et al.
(författare)
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X-ray photoemission and Auger electron spectroscopy analysis of fast responding activated metal oxide silicon carbide gas sensors
- 1997
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 299:1-2, s. 183-189
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Tidskriftsartikel (refereegranskat)abstract
- Platinum-silicon dioxide-silicon carbide, MOSiC, sensors are possible to operate at high temperatures and show a gas sensitivity pattern which is of interest for many applications including exhaust gases from car engines. The introduction of a buffer layer of tantalum silicide between the metal and the silicon dioxide resulted, after an annealing step, in a very good adhesion of the gate contact and fast responding sensors with improved signal stability. Depth profiling using X-ray photoemission and Auger electron spectroscopy showed that the annealing step converts the tantalum silicide to a mixed phase predominantly containing tantalum pentoxide. Tantalum silicide as well as platinum silicide are also present in the metal-oxide interface region.
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| 2. |
- Zubkans, J., et al.
(författare)
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In-situ modification of the NOx sensitivity of thin discontinuous platinum films as gates of chemical sensors
- 1995
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 268:1-2, s. 140-143
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Tidskriftsartikel (refereegranskat)abstract
- It is shown how chemically sensitive metal-oxide semiconductor field-effect transistors with a thin discontinuous platinum gate can be modified for the detection of NOx. After a pulse of ammonia the sensors show an increased sensitivity to NOx. The threshold voltage shift induced by NOx is opposite to the direction before the ammonia pulse. The threshold voltage now increases due to NOx exposure, while hydrogen, ammonia and hydrocarbons cause a decrease of the threshold voltage. The temperature dependence of the NOx sensitivity suggests that after the ammonia pulse there are two competing polarisation phenomena caused by the interaction between NOx and the sensing surface. The results are of general interest since they indicate how thin sensing layers can be modified after fabrication to promote sensitivity towards specific molecules. Furthermore they shed some new light on the detection mechanisms of thin discontinuous metal gates.
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| 3. |
- 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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| 4. |
- Khranovskyy, Volodymyr, et al.
(författare)
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Effect of oxygen exposure on the electrical conductivity and gas sensitivity of nanostructured ZnO films
- 2009
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 517:6, s. 2073-2078
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured ZnO films (Undoped and Ga, Co, Mn doped) were exposed to oxygen (1-80 vol.%) at temperature range of 300-500 degrees C in order to reveal the ambience-temperature effect oil the electrical conductivity. The dominant effect of ambient influence via oxygen absorption was observed: the intensity of conductivity decrease was found to be proportional with temperature and tends to saturate with time. It is demonstrated that oxygen absorption occurs accordingly to diffusion law and the quantifying of oxygen diffusion was realized for different samples. It is revealed that the type of dopant affects the diffusion in ZnO and the tendency to increase the diffusion intensity with dopant content has been observed. After oxygen saturation the reversible effect of oxygen adsorption became dominant and contributed to the films conductivity. Oxygen exposure undoped ZnO films revealed high sensitivity for oxygen content change in the ambience therefore they have been preceded further for gas sensor design and the detailed investigation of films sensing properties has been carried out.
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| 5. |
- Lewin, Erik, et al.
(författare)
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Carbide and nanocomposite thin films in the Ti-Pt-C system
- 2010
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Ingår i: Thin Solid Films. - : Elsevier B.V.. - 0040-6090 .- 1879-2731. ; 518:18, s. 5104-5109
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Tidskriftsartikel (refereegranskat)abstract
- Thin films in the Ti-Pt-C system were deposited by non-reactive, DC-magnetron sputtering. Samples were characterised using X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy. A previously not reported metastable solid solution carbide, (Ti1-xPtx)C-y with a Pt/Ti ratio of up to 0.43 was observed. This solid solution phase was present both as single phase in polycrystalline samples, and together with amorphous carbon (a-C) in nanocomposite samples. Annealing of nanocomposite samples leads to the decomposition of the solid solution phase and the formation of a nc-TiCx/a-C/nc-Pt nanocomposite. Test sensors for automotive gas exhausts manufactured from such a three-phase material suffer from complete oxidation of the coating at 400 degrees C with no observed sensor activity.
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