Room-temperature semiconductor gas sensor based on nonstoichiometric tungsten oxide nanorod film

Porous tungsten oxide films were deposited onto a sensor substrate with a Si bulk-micromachined hotplate, by drop-coating isopropyl alcohol solution of highly crystalline tungsten oxide ( W O 2.72 ) nanorods with average 75 nm length and 4 nm diameter. The temperature-dependent gas sensing characteristics of the films have been investigated over the mild temperature range from 20 to 250 ° C . While the sensing responses for ammonia vapor showed increase in electrical conductivity at temperatures above 150 ° C as expected for n -type metal oxide sensors, they exhibited the opposite behavior of unusual conductivity decrease below 100 ° C . Superb sensing ability of the sensors at room temperature in conjunction with their anomalous conductivity behavior might be attributed to unique nanostructural features of very thin, nonstoichiometric W O 2.72 .