US5448906A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ambient temperature gas sensor
Assignee: Boeing North American Inc
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Filing: 1994-07-26
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Granted: 1995-09-12
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Expires: 2014-07-26
Abstract
Abstract An ambient temperature solid state sensor for detecting the concentration of a gas includes an insulating substrate, a polycrystalline semiconducting oxide thin film deposited on the substrate such that the gas can be adsorbed on the surface of the film, the film having a low carrier concentration and a high resistivity, a pair of electrodes disposed on the film for measuring the electrical resistance of the film, and a source of light having a wavelength component which is absorbed by the thin film, thereby causing photodesorption of the gas from the surface of the film and establishing the equilibrium between gaseous species in the ambient and gaseous species adsorbed on the oxide surface. The resistance of the thin film is dependent on the amount of adsorbed gas, the measured resistance of the film thereby indicating the concentration of the gas.
Inventors
- 👤 Jeffrey T. Cheung
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:56
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/12
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
161 words
An ambient temperature solid state sensor for detecting the concentration of a gaseous species in an ambient environment, comprising: an enclosure; an insulating substrate mounted within the enclosure; a polycrystalline semiconducting oxide thin film deposited on the substrate such that the gaseous species to be detected can be adsorbed on the surface of the film, the film having a low carrier concentration and a high resistivity; a pair of electrodes disposed on the film for measuring the electrical resistance of the film; and a source of light, directed toward the film and having a wavelength component which is absorbed by the thin film, thereby causing photodesorption of the adsorbed gaseous species from the surface of the film, establishing an equilibrium between the gaseous species in the environment and the adsorbed gaseous species, and changing the resistance of the film, measured across the electrodes, the measured resistance of the film thereby indicating the concentration of the gaseous species in the ambient environment.
Claim 2
Dependent Claim
161 words
An ambient temperature solid state sensor for detecting the concentration of a gaseous species in an ambient environment, comprising: an enclosure; an insulating substrate mounted within the enclosure; a polycrystalline semiconducting oxide thin film deposited on the substrate such that the gaseous species to be detected can be adsorbed on the surface of the film, the film having a low carrier concentration and a high resistivity; a pair of electrodes disposed on the film for measuring the electrical resistance of the film; and a source of light, directed toward the film and having a wavelength component which is absorbed by the thin film, thereby causing photodesorption of the adsorbed gaseous species from the surface of the film, establishing an equilibrium between the gaseous species in the environment and the adsorbed gaseous species, and changing the resistance of the film, measured across the electrodes, the measured resistance of the film thereby indicating the concentration of the gaseous species in the ambient environment.
Claim 3
Dependent Claim
16 words
The sensor of claim 1, wherein the gaseous species to be detected comprises an oxidizing gas.
Claim 4
Dependent Claim
16 words
The sensor of claim 2, wherein the oxidizing gaseous species to be detected further comprises oxygen.
Claim 5
Dependent Claim
31 words
The sensor of claim 1, wherein the thin film further comprises a polycrystalline semiconducting oxide thin film having a nominal electrical resistance less than 1 megohms between the pair of electrodes.
Claim 6
Dependent Claim
19 words
The sensor of claim 4, wherein the thin film further comprises a fine grain polycrystalline semiconducting oxide thin film.
Claim 7
Dependent Claim
21 words
The sensor of claim 5, wherein the thin film is selected from the group consisting of tin oxide and zinc oxide.
Claim 8
Dependent Claim
28 words
The sensor of claim 6, wherein the thin film further comprises a thin film doped with an extrinsic impurity to reduce the electron carrier density of the film.
Claim 9
Dependent Claim
20 words
The sensor of claim 7, wherein the thin film further comprises zinc oxide and the extrinsic impurity dopant comprises nitrogen.
Claim 10
Dependent Claim
17 words
The sensor of claim 1, wherein the source of light further comprises a source of ultraviolet light.
Claim 11
Dependent Claim
16 words
The sensor of claim 1, wherein the source of light further comprises a light emitting diode.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-09-11 | 1999-03-13 | 1999-09-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-09-11 | 2003-03-13 | 2003-09-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-09-11 | 2007-03-13 | 2007-09-12 | $7700.00 | Window Closed / Lapsed |