NO2 SENSITIVE LAFEO3 THIN-FILMS PREPARED BY RF-SPUTTERING

LaFeO3 thin films with different thicknesses have been fabricated by the r.f. magnetron sputtering method on Al2O3 substrates with comb-type Au electrodes. The influence of annealing temperatures and times on the NO2 sensitivity of the thin films has been investigated. The thin films are annealed at temperatures from 600 to 1000 degrees C in flowing air for 30 or 60 min. The conductivity of thin films increases noticeably when NO2 gas is introduced into the measuring chamber, and returns to its original level after NO2 is removed. The NO2 response curve of LaFeO3 thin films shows two distinct phases: an initial fast and large conductivity change, followed by a much slower change. These phases are attributed to the surface chemisorption process of NO2 and the oxidation process of the bulk, respectively. The material's structure plays a fundamental role in its NO2 response, while the influence of film thickness is less important. The annealing temperature and time of LaFeO3 sputtered thin films determine their NO2 sensitivity. The thinner films show higher resistivities, slightly greater NO2 sensitivities and less stable results.