Laser induced local and periodic phase transformations in iron oxide thin films obtained by chemical vapour deposition

Iron oxide films have been deposited on Si(100) substrates by chemical vapour deposition (CVD) of iron(III) tert-butoxide ([Fe(OtBu)3]2) in the temperature range 350–450 8C. The precursor flux and substrate temperature were varied to control the phase composition, average grain size and film thickness. The nature of substrate and deposition temperature markedly influence the morphology and iron-oxygen stoichiometry in the CVD deposits. Phase transformations in iron oxide films were achieved through precise local and periodic heating of the films by interfering laser beams. The interaction of iron oxide films with short laser pulses (Nd:YAG, 355 nm) induced partial transformation of hematite (a-Fe2O3) to magnetite (Fe3O4) or magnetite to wu¨ stite (Fe1 xO), respectively. The phase characterization and morphology of the hematite and magnetite films were investigated before and after laser irradiation by X-ray diffractometry, high resolution scanning electron microscopy and white light interferometry