A route to high sensitivity and rapid response Nb 2O 5-based gas sensors: TiO 2 doping, surface embossing, and voltage optimization

Abstract

We report a novel route for the fabrication of highly sensitive and rapidly responding Nb 2O 5-based thin film gas sensors. TiO 2 doping of Nb 2O 5 films is carried out by co-sputtering without the formation of secondary phases and the surface area of TiO 2-doped Nb 2O 5 films is increased via the use of colloidal templates composed of sacrificial polystyrene beads. The gas sensitivity of Nb 2O 5 films is enhanced through both the TiO 2 doping and the surface embossing. An additional enhancement on the gas sensitivity is obtained by the optimization of the bias voltage applied between interdigitated electrodes beneath Nb 2O 5-based film. More excitingly, such a voltage optimization leads to a substantial decrease in response time. Upon exposure to 50 ppm CO at 350 °C, a gas sensor based on TiO 2-doped Nb 2O 5 film with embossed surface morphology exhibits a very high sensitivity of 475% change in resistance and a rapid response time of 8 s under 3 V, whereas a sensor based on plain Nb 2O 5 film shows a 70% resistance change and a response time of 65 s under 1 V. Thermal stability tests of our Nb 2O 5-based sensor reveal excellent reliability which is of particular importance for application as resistive sensors for a variety gases.