An iron(II) diketonate-diamine complex as precursor for thin film fabrication by atomic layer deposition

A new divalent Fe precursor has been explored for deposition of iron-containing thin filmsby atomic layer deposition and molecular layer deposition (ALD/MLD). The Fe(II) beta-diketonate-diamine complex, Fe(hfa)2TMEDA, (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate, TMEDA = N,N,N,N-tetramethylethylenediamine) can be handled in air, and sublimation at 60oC ensures a satisfactoryvaporization rate. The reactivity of the precursor does not allow for direct reaction with water as co-reactant. Nevertheless, it reacts with carboxylic acids, resulting in organic-inorganic hybrid materials, andwith ozone, yielding alpha-Fe2O3. The divalent oxidation state of iron was maintained during deposition whenoxalic acid was used as co-reactant, demonstrating the first preservation of Fe(II) from precursor to filmduring an MLD process. A self-saturating growth mode was proven by in situ quartz crystal microbalance(QCM) measurements, and the films were further characterized by grazing incidence X-ray diffraction(GIXRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS).