Iron oxide thin films prepared by ion beam induced chemical vapor deposition: Structural characterization by infrared spectroscopy

Iron oxide thin films as hematite (α-Fe2O3) have been prepared by ion beam induced chemical vapor deposition. Very compact and dense films are obtained by this procedure. The thin films have been grown by ombardment of the substrate surfaces with O2+ ions or mixtures of O2+ and Ar+ ions, while a volatile precursor of iron [i.e., Fe(CO)5] is dosed onto the substrate surface. In the latter case, Ar atoms are incorporated within the iron oxide lattice. Atomic force microscopy, Rutherford backscattering spectroscopy, and x-ray photoelectron spectroscopy were utilized to characterize the films' surface morphology, stoichiometry and chemical state. The film structure has been analyzed by grazing angle x-ray diffraction (XRD) and infrared spectroscopies. In particular, infrared spectroscopy has permitted a thorough structural characterization of the films, even in the cases where XRD does not provide information about the structure. Thus, when O2 1 ions are used for the synthesis, iron oxide thin films grow with a hematite structure with the c axis of the crystallites perpendicular to the film surface. However, when an Ar+/O2+ ion mixture is used, the thin films have a hematite structure with the c axis of the crystallites oriented parallel to the film surface.