Atomic Layer Deposition of NiO by the Ni(thd)2/H2O Precursor Combination

Polycrystalline nickel oxide is deposited on SiO2 substrates by alternating pulses of bis(2,2,6,6-tetramethylheptane-3,5-dionato)nickel(II) (Ni(thd)(2)) and H2O. The deposition process shows atomic layer deposition (ALD) characteristics with respect to the saturation behavior of the two precursors at deposition temperatures up to 275 degrees C. The growth of nickel oxide is shown to be highly dependent on surface hydroxide groups, and a large excess of H2O is required to achieve saturation. Throughout the deposition temperature range the amount of carbon in the film, originating from the metal precursor ligand, is in the range 1-2%. Above 275 degrees C ALD growth behavior is lost in favor of thermal decomposition of the metal precursor. The initial nucleation process is studied by atomic force microscopy (AFM) and reveals nucleation of well-separated grains which coalesce to a continuous film after about 250 ALD cycles.