Synthesis and Characterization of BiFeO₃ Thin Films for Multiferroic Applications by Radical Enhanced Atomic Layer Deposition

A radical-enhanced atomic layer deposition (RE-ALD) process is described for the synthesis of BiFeO 3 . Metalorganic precursors β-diketonate, tris(2,2,6,6-tetramethyl-3,5-heptanedionato) iron(III) (Fe(TMHD) 3 ), and Bi(TMHD) 3 are coreacted with oxygen radicals (produced by a coaxial microwave cavity) as the oxidation source. Stoichiometric BiFeO 3 films were deposited on SrTiO 3 (001) substrates at 210 °C and crystallized from 450 to 750 °C. The crystallinity and phases in the films were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The BiFeO 3 was determined to be phase-pure and epitaxial when annealed at 650 °C. To study the functional properties, ferroelectric switching was demonstrated using piezoresponse force microscopy (PFM), while weak ferromagnetic behavior was measured using superconducting quantum interference device (SQUID) magnetometry. The films have properties comparable to those of films grown by other methods—growth rates are superior in comparison to other ALD methods, demonstrating the potential of RE-ALD for the synthesis of multiferroic complex–oxide thin films.