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

Indium tin oxide (ITO) thin-fllm-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 Alms deposited on a quartz substrate, with a substrate temperature Ts of 100°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°C, are observed. This performance is superior to other previously reported ITO thin-fllm-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.