Thin films of In₂O₃/SiO for Humidity Sensing Applications

Abstract: This paper documents the manufacture and testing of a humidity sensor based on a combination of In₂O₃/SiO. A number of different sensor samples have been produced by thermal deposition and the effect of varying the vacuum pressure has also been investigated. The AC and DC conduction mechanisms have been investigated. From the AC conduction studies, the tunneling conduction mechanism has been observed at low frequencies and the hopping conduction mechanism, for the majority of sensor samples, has been observed at high frequencies. The DC conduction mechanisms have indicated the possibility of spacecharge-limited conduction. The sensor with the highest humidity sensitivity of 1.145%/RH% is 85%In₂O₃/15%SiO, which is produced at a vacuum pressure of 2×10^-4 mbar.From the point of view of temperature stability, the 55%In₂O₃/45%SiO samples produced at a vacuum pressure of 2×10^-4 mbar exhibit the lowest temperature sensitivity, 0.3%/oC.