Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing gas sample
Patent
1997-03-13
1998-10-20
Warden, Jill
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing gas sample
422 94, 422 95, 422 96, 422 97, 436134, 436137, 436141, 436149, 436153, 73 232, 73 2331, 73 3106, 338 34, G01N 27403
Patent
active
058242716
DESCRIPTION:
BRIEF SUMMARY
FIELDS OF THE INVENTION
The invention relates to a gas sensor based on gallium oxide, for the detection of oxidizing or reducing gases.
BACKGROUND OF THE INVENTION
Gallium oxide sensors are known and are disclosed in EP 0 464 243 "oxygen sensor with semiconducting gallium oxide" and EP 0 464 244 "sensor for the detection of reducing gases". The electrical resistance, and also the gas sensitivity, of Ga.sub.2 O.sub.3 are strongly temperature-dependent. In order to obtain a gas-sensitive effect, Ga.sub.2 O.sub.3 gas sensors must be operated in a gas-specific temperature range. Currently available Ga.sub.2 O.sub.3 gas sensors need to be thermally regulated very accurately to within this range, so that a temperature fluctuation does not induce the same resistance change as would have been caused by a change in the concentration of the gas to be detected. In order to ensure a sufficiently constant operating temperature, a highly elaborate hardware outlay is necessary. The sensitivity of the overall system is strongly limited by the remaining system deviation. In the case of strong and frequent temperature fluctuations, signal evaluation is only conditionally possible, since the control system reacts only after a delay.
If a part of the sensor arrangement is covered with a gas-impermeable layer, in order to use this part, which is thereby passivated, for temperature compensation, as is disclosed in the refinements of EP 0 464 243 or EP 0 464 244, the following problem arises. The originally gas-impermeable layer, which is applied to a gas-sensitive part in order to cover it, becomes cracked and therefore gas-permeable over time. That part of the sensor arrangement which is intended only to be temperature-dependent also becomes gas-sensitive as a result of the gas which penetrates the cover layer through the cracks, which greatly vitiates the measurement.
A further possibility of using a part of the sensor arrangement for temperature compensation consists in doping it with metal atoms, for example gold, so heavily that it loses its gas sensitivity. This is described in DE 42 10 397 or DE 42 10 398. A disadvantage with this is that the doped part of the sensor arrangement is not stable.
SUMMARY OF THE INVENTION
The object of the invention is to provide a gas sensor which provides two output signals, one of them having gas dependence and temperature dependence, and the other merely having the temperature dependence.
A suitable combination of the two output signals advantageously provides a compensated signal which is independent of temperature fluctuations.
The present invention provides a gas sensor that comprises a substrate that carries a first electrode and a second electrode. The electrodes are preferably disposed on the substrate adjacent to one another. The first electrode is further disposed between the substrate and a gas-sensitive component, in the form of an arrangement, housing or structure. The gas-sensitive component comprises an end-type semiconductor and further has a resistance that is gas-dependent as well as temperature-dependent.
The second electrode of the present invention is disposed between the substrate and a non-gas-sensitive component, also in the form of an arrangement, housing or structure. The non-gas-sensitive component comprises an n-type semiconductor and a p-type semiconductor and further has a resistance that is temperature-dependent but that is not gas-dependent.
In an embodiment, the n-type semiconductor of the gas-sensitive component is Ga.sub.2 O.sub.3.
In an embodiment, the n-type semiconductor of the non-gas-sensitive component is Ga.sub.2 O.sub.3.
In an embodiment, the n-type semiconductor of the non-gas-sensitive component is Ga.sub.2 O.sub.3 and the p-type semiconductor of the non-gas-sensitive component is ZrO.sub.2.
In an embodiment, the n-semiconductor of the non-gas-sensitive component is at least one layer of n-type semiconductor material and the p-semiconductor of the non-gas-sensitive component is at least one layer of p-type semiconductor material. In a pre
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Fleischer Maximilian
Frank Joachim
Meixner Hans
Carrillo Sharidan
Siemens Aktiengesellschaft
Warden Jill
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