Effect of Air-Pressure on Room Temperature Hydrogen Sensing Characteristics of Nanocrystalline Doped Tin Oxide MEMS-Based Sensor

Abstract

Nanocrystalline indium oxide (In₂O₃)-doped tin oxide (SnO₂) thin film sensor has been sol–gel dipcoated on a microelectrochemical system (MEMS) device using a sol–gel dip-coating technique. Hydrogen (H₂) at ppm-level has been successfully detected at room temperature using the present MEMS-based sensor. The room temperature H₂ sensing characteristics (sensitivity, response and recovery time, and recovery rate) of the present MEMS-based sensor has been investigated as a function of air-pressure (50–600 Torr) with and without the ultraviolet (UV) radiation exposure. It has been demonstrated that, the concentration of the surface-adsorbed oxygen-ions (which is related to the sensor-resistance in air), the ppm-level H₂, and the oxygen (O₂) partial pressure are the three major factors, which determine the variation in the room temperature H₂ sensing characteristics of the present MEMS-based sensor as a function of air-pressure.