# US 7,406,856 B2 · Chromium/titanium oxide semiconductor gas sensor and method for production thereof

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- Number: US 7,406,856 B2
- Document ID: US7406856B2
- Status: Granted
- Kind: B2
- Application number: 10/489,574
- Filed: 2002-09-02
- Published: 2004-11-25
- Granted: 2008-08-05
- Earliest claimed: 2001-09-12
- Assignees: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
- Inventors: Harald Bottner; Jurgen Wollenstein; Gerd Kuhner
- Web page: https://patentgrep.com/patent/US7406856B2

## CPC

- G01N 27/125: {Composition of the body, e.g. the composition of its sensitive layer}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A metal oxide semiconductor gas sensor and a method for production thereof. The sensor comprises a sensor-active metal oxide thin layer applied to a substrate, in contact with at least one electrode. The sensor-active metal oxide thin layer comprises a chromium/titanium oxide (CTO) layer with a thickness of about 10 nm to about 1 μm. The chromium and titantium layers are applied over each other using thin layer technology and are subsequently tempered.

## Claims

### Claim 1

A metal oxide semiconductor gas sensor comprising a sensor-active thin metal oxide layer that is applied to a substrate, and that is in contact with at least one electrode wherein the sensor-active thin metal oxide layer is a chromium/titanium oxide (CTO) layer with a layer thickness of 100 nm to 500 nm, whereby the mixed oxide is present in the form of a single phase material having a corundum structure.

### Claim 2 (depends on 1)

The metal oxide semiconductor gas sensor in accordance with claim 1 wherein the CTO layer has up to 40 atom-% of titanium in the cation sub-lattice.

### Claim 3 (depends on 1)

The metal oxide semiconductor gas sensor in accordance with claim 1 wherein the CTO layer has an overall resistance of 5 kΩ to 10 MΩ at about 350° C.

### Claim 4 (depends on 3)

The metal oxide semiconductor gas sensor in accordance with claim 3 wherein the overall resistance is in the 10-500 kΩ range.

### Claim 5 (depends on 1)

The metal oxide semiconductor gas sensor in accordance with claim 1 wherein at least in part, the CTO layer contains at least one of a catalyst and a promoter.

### Claim 6 (depends on 1)

The metal oxide semiconductor gas sensor in accordance with claim 1 wherein the substrate comprises at least one of silicon, A12O3, sapphire and quartz glass.

### Claim 7 (depends on 1)

The metal oxide semiconductor gas sensor in accordance with claim 1 further comprising a passivation layer between the substrate and the CTO layer.

### Claim 8 (depends on 7)

The metal oxide semiconductor gas sensor in accordance with claim 7 wherein the passivation layer comprises at least one of SiO2, Si3N4, A12O3.

### Claim 9 (depends on 8)

The metal oxide semiconductor gas sensor in accordance with claim 8 wherein the passivation layer has a layer thickness of from about 100 nm to about 1 μm.

### Claim 10 (depends on 1)

The metal oxide semiconductor gas sensor in accordance with claim 1 wherein the sensor is constructed in the form of a contact pad that is applied to the substrate.

### Claim 11 (depends on 1)

A sensor array comprising a plurality of metal oxide semiconductor gas sensors constructed according to claim 1 coupled together to form the sensor array.

### Claim 12 (depends on 11)

A sensor array according to claim 11 comprising at least two rows arranged in parallel containing a combined total of 3-10,000 metal oxide semiconductor gas sensors.