Indium-gallium–zinc oxide (IGZO) thin-film gas sensors prepared via post-deposition high-pressure annealing for NO2 detection

Indium–gallium–zinc oxide (IGZO) thin films were prepared in a N2 environment by varying the annealing pressure and then tested for NO2 gas detection. These thin films, whose average thickness ranged between 5 and 100 nm, were deposited via the sputtering on alumina substrates equipped with interdigitated Au electrodes using an IGZO polycrystalline target (ZnO: Ga2O3:In2O3 = 1:1:1 mol%). The effects of annealing pressure and environment were investigated. A superior sensor response (S) was observed when increasing the annealing pressure; the prepared IGZO thin film showed an S of –800 at an operating temperature of 250 °C for 25 ppm NO2 gas. The recovery time decreased with increasing the annealing temperature. The sensor annealed at 400 °C at 3 atm showed superior selectivity to various gases and longtime stability of 60 days was attained. The role of the oxygen vacancies in the sensor performance was also investigated.