Characterization and gas-sensing behavior of an iron oxide thin film prepared by atomic layer deposition

In this work we investigate an iron oxide thin film grown with atomic layer deposition for a gas sensor application. The objective is to characterize the structural, chemical, and electrical properties of the film, and to demonstrate its gas-sensitivity. The obtained scanning electron microscopy and atomic force microscopy results indicate that the film has a granular structure and that it has grown mainly on the glass substrate leaving the platinum electrodes uncovered. X-ray diffraction results show that iron oxide is in the alpha-Fe2O3 (hematite) phase. X-ray photoelectron spectra recorded at elevated temperature imply that the surface iron is mainly in the Fe3+ state and that oxygen has two chemical states: one corresponding to the lattice oxygen and the other to adsorbed oxygen species. Electric conductivity has an activation energy of 0.3-0.5 eV and almost Ohmic current-voltage dependency. When exposed to O-2 and CO, a typical n-type response is observed. (C) 2007 Elsevier B.V. All rights reserved.