Effect of film thickness on the electrical and ethanol sensing characteristics of LaFeO3 nanoparticle-based thick film sensors

LaFeO3 nanoparticles were prepared by a sol-gel method and chosen as sensing material. A series of thick film sensors were fabricated with one to six layers of LaFeO3 nanoparticles in the thickness of 40-234 pm, so as to study the effect of film thickness on the electrical and ethanol sensing characteristics of LaFeO3 nanoparticle-based thick film sensors. FE-SEM was used to measure the film thickness, and to characterize surface morphology and microstructure inside the sensing matrix. The reduced resistance with increasing film thickness is macroscopically ascribed to the increment of cross-section area for the flowing of charge carriers and is microscopically attributed to the reduction of activation energy for the hopping of small polarons. As for the sensing performance towards ethanol, i.e. prime working temperature, gas response, dynamic response, and gas selectivity, the optimal film thickness depends on the required sensor parameters. Taken together, the sensor with the film thickness of approximately 117 mu m showed the best performance, with a fast dynamic response, high gas response and satisfactory selectivity.