Room Temperature Gas Sensor with a High Sensitivity to Hydrogen Based on SnO2Films Prepared by Photochemical Techniques

Resistive gas sensors with a high sensitivity to hydrogen at room temperature were fabricated. SnO2 films were deposited by photochemical deposition using an SnSO4 solution, and Pd was doped by photochemical doping using a PCl2 solution. An interdigit Au electrode was formed, and then the samples were annealed in nitrogen atmosphere at various temperatures. The sensitivity and response speed depended on the annealing temperature. For the sample annealed at 200 °C, the conductivity increased by a factor of 104 upon exposure to 5000 ppm hydrogen within 1 min. The transient response was analyzed using a simple theoretical model. The sensor current was shown to be controlled by a Schottky barrier at grain boundaries, and the transient response was well fitted by a double-exponential function.