SnO_2 film with bimodal distribution of nano-particles for low concentration hydrogen sensor: Effect of firing temperature on sensing properties

摘要

Spin coated sensor films of nano-SnO_2 with bimodal nano-size particle distribution were obtained through thermal decomposition of SnCl_2 using a simple and fast single step thermal decomposition technique. The deposition was done on soda-lime glass substrates using variable decomposition/firing temperature in the range of 400-600℃ at the interval of 50℃. The effect of firing temperature on structural, micro-structural and optical properties was studied by X-ray diffractometer (XRD), atomic force microscopy (AFM) and UV-Vis respectively. AFM study of the films revealed a special type of microstruc-ture i.e. conducting larger globules of 8-20 nm with smaller nanoparticles of ≤3 nm on the surface of the bigger globules. The films fired at 400℃ exhibit the highest UV absorption peak compared to other samples. A highest response (R_(air)/R_(gas) = 24) to 300 ppm of H_2 is recorded for films fired at 550℃ and they exhibit sensitivity of ～90 × 10~(-3) for concentration of H_2 (1-20 ppm). These sensors also exhibit good stability of resistance at the optimized operating temperature of 265℃ and in the presence of different relative humidity (RH=20 -100%).