INFRARED PROPERTIES OF IRON-OXIDE FILMS GROWN BY PULSED-LASER DEPOSITION

Epitaxial magnetite (Fe3O4) thin films were grown on MgO(001) substrat es by pulsed laser deposition. The Fe3O4 films were transformed into o ther iron oxide films by annealing under different conditions of oxyge n pressure. Far- and mid-infrared reflectance spectra were measured be tween 50 and 4000 cm(-1). The Fe3O4 films were found to have a broad i nfrared spectral weight which was attributed to hopping of small polar ons between iron ions. The infrared reflectance measurement was also f ound to be useful to identify the alpha-Fe2O3 phase which is difficult to probe using conventional X-ray diffraction techniques. By fitting the infrared spectra using the effective medium approximation, the vol ume fractions of the Fe3O4 and the alpha-Fe2O3 phases in the annealed films were estimated.