High-Sensitivity Humidity Sensor Based on a Single Sb-Doped SnO₂ Whisker

Sb-doped SnO₂ whiskers were prepared by thermal evaporation of mixture of SnO and Sb₂O₃ powders. Sb segregation to the surface of SnO₂ whisker was demonstrated. The humidity sensitive characteristics of single SnO₂ whisker-based sensors have been investigated. By monitoring the current through the SnO₂ whisker at fixed voltage, relative humidity can be determined. It is found that the current of the Sb-doped SnO₂ whisker-based sensor increases by about five orders of magnitude with increasing relative humidity (RH) from 43.2 to 84.3%. The response and recovery time of the sensor are approximate 12 and 8 s, respectively. Compared to the pure SnO₂ whisker, Sb-doped SnO₂ whisker exhibits greatly improvement of sensitivity which could be explained by the surface-segregated Sb atoms. This is the first step towards fundamental understanding of single-crystalline tin oxide whiskers for sensor applications, which could lead to integration in real devices.