XPS and UV-VIS study of high-purity Fe2O3 thin films obtained using the sol-gel technique

Fe2O3 thin films obtained by the sol-gel technique from ethanolic solutions of Fe(OEt)3 have been deposited on pure silica and heat treated at two different temperatures. Preliminary thermogravimetric (TG) measurements on the precursor were carried out in order to evaluate the weight loss as a function of temperature and heat-treatment time. Chemical characterization of the films was obtained by XPS and UV-VIS spectroscopies. The bulk of the film heated at 500 °C did not show residual carbon. The corresponding UV-VIS spectrum was well structured in the 15 000-50 000 cm-1 region due to charge-transfer and inner-oxygen transitions. XRD measurements showed an amorphous pattern for the sample heated at 200 °C, whereas a diffraction peak corresponding to haematite (?-Fe2O3) nanocrystals was observed for the film heated at 500 °C.