Ammonia Sensing Characteristics of Sputtered Indium Tin Oxide (ITO) Thin Films on Quartz and Sapphire Substrates

Indium tin oxide (ITO) thin-film-based ammonia sensors on sapphire and quartz substrates, fabricated by radio-frequency sputtering with substrate heated treatments, are studied and demonstrated. Experimentally, good NH3 sensing properties of ITO thin films deposited on a quartz substrate, with a substrate temperature T-s of 100 degrees C, including a high sensitivity ratio of 2312%, and fast response and recovery times of 73 and 104 s upon the introduction of a 1000-ppm NH3/air gas at 150 degrees C, are observed. This performance is superior to other previously reported ITO thin-film-based ammonia sensors. Moreover, a good logarithmic linear relationship between the sensitivity ratio and the NH3 concentration is found. Therefore, based on the advantages of simple structure, easy operation, low cost, and excellent properties, the studied device gives a promise for high-performance ammonia sensing applications.