Gas-sensitive device

• US 5,086,286 A
• Filed: 07/26/1990
• Issued: 02/04/1992
• Est. Priority Date: 07/28/1989
• Status: Expired due to Fees

• Current Assignee: Kurabo Industries Limited
• Original Assignee: Kurabo Industries Limited
• Inventors: Yasukawa, Yoshikazu, Inagaki, Norihiro
• Primary Examiner(s): Lateef, Marvin M.
• Application Number:
  US07/563,321
• Time in Patent Office: 558 Days
• Field of Search: 338/34, 338/35, 422/98, 502/339, 502/325, 427/419.1, 427/419.2, 73/23.2, 73/23.22, 73/31.05, 73/31.06, 73/23.25
• US Class Current: 338/34
• CPC Class Codes: G01N 27/12 of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid , for detecting components in the fluid
• CPC Class Codes: G01N 33/004 CO or CO2
• CPC Class Codes: H01C 7/00 Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material consisting of loose powdered or granular material H01C8/00; resistors having potential barriers, e.g. field-effect resistors, H01L29/00; semiconductor devices sensitive to electromagnetic or corpuscular radiation, e.g. photoresistors, H01L31/00; magnetic field controlled resistors H10N50/10; bulk negative resistance effect devices H10N80/00

Abstract

A thin film gas-sensitive device includes an insulating substrate having a pair of electrodes, a gas-sensitive layer having a gas sensitive substance deposited on the insulating substrate and electrodes, and a catalytic layer deposited on the gas-sensitive layer and insulating substrate as a non-continuous layer. The insulating substrate is partly uncovered because the electrodes, the gas-sensitive layer containing the gas-sensitive substance and the catalytic layer do not thoroughly cover the substrate.

Claims

1. A thin film gas-sensitive device comprising:

an insulating substrate having a pair of electrodes disposed theron;

a gas-sensitive layer, having a gas sensitive substance, deposited on the insulating substrate and electrodes; and

a catalytic layer deposited on the gas-sensitive layer and insulating substrate as a non-continuous layer;

wherein the insulating substrate is partly uncovered because the electrodes, the gas-sensitive layer containing the gas-sensitive substance and the catalytic layer do not thoroughly cover the substrate.

2. A gas-sensitive device according to claim 1, wherein the gas-sensitive substance comprises at least one of SnO₂ or In₂ O₃.

3. A gas-sensitive device according to claim 1 for use in detecting CO-gas, wherein the device contains less than 900 parts by weight of Au per 100 parts by weight of Sn in the gas-sensitive layer.

4. A gas-sensitive device according to claim 1, wherein the catalytic layer is of an average thickness of 5 nm or less and comprises at least one of Pt and Pd.

5. A gas-sensitive device according to claim 3, wherein the gas sensitive layer contains Sn in the form of SnO₂.

6. A gas sensitive device according to claim 1, wherein the electrodes are comb-shaped.

7. A gas-sensitive device comprising:

an insulating substrate;

a pair of electrodes disposed on the substrate;

a gas-sensitive substance deposited on portions of the substrate and the electrodes such that the substrate and the electrodes are only partially covered by the gas-sensitive substance; and

a catalyst deposited on portions of the gas-sensitive substance and the substrate such that the gas-sensitive substance and the substrate are only partially covered by the catalyst.

8. The gas-sensitive device of claim 7, wherein the gas-sensitive substance comprises at least one of SnO₂ or In₂ O₃.

9. The gas-sensitive device of claim 7, wherein the gas-sensitive substance comprises a mixture of Au and SnO₂, the mixture being less than 900 parts by weight of Au per 100 parts by weight of Sn.

10. The gas-sensitive device of claim 7, wherein the catalyst is one of Pt and Pd.

11. The gas-sensitive device of claim 10, wherein the catalyst is deposited as a non-continuous layer having an average thickness of no more than 5 nm.

12. A method of producing the gas-sensitive device according to claim 7, comprising:

providing the insulating substrate;

forming the pair of electrodes on the substrate;

depositing a selected average thickness of the gas-sensitive substance in a vacuum on the electrodes and substrate;

thermally treating the gas-sensitive substance to oxidize the gas-sensitive substance; and

depositing a selected average thickness of the catalyst on the substrate and gas-sensitive substance.

13. The method according to claim 12, wherein the average thickness of the gas-sensitive substance is 13 nm.

14. The method according to claim 12, wherein the average thickness of the catalyst is 5 nm.

15. The method according to claim 12, wherein during depositing of the gas-sensitive substance and the catalyst, the selected average thicknesses are measured using a crystal oscillator.

16. The method according to claim 12, wherein depositing a selected average thickness of the gas-sensitive substance in a vacuum on the electrodes and substrate comprises:

depositing less than 900 parts by weight of Au; and

depositing 100 parts by weight of Sn,

and wherein during the step of thermally treating the gas-sensitive substance to oxidize the gas-sensitive substance, SnO₂ is formed and the Au mixes with the SnO₂.