Film microstructure-deposition condition relationships in the growth of epitaxial NiO films by metalorganic chemical vapor deposition on oxide and metal substrates

High-quality epitaxial or highly textured NiO thin films can be grown at temperatures of 400-750 °C by low-pressure metalorganic chemical vapor deposition (MOCVD) on MgO, SrTiO₃, C-cut sapphire, as well as on single crystal and highly textured Ni (200) metal substrates using Ni(dpm)₂ (dpm = dipivaloylmethanate) as the volatile precursor and O₂ or H₂O as the oxidizer/protonolyzer. X-ray diffraction (XRD), scanning electron microscopy/energy dispersive detection (SEM/EDX), and atomic force microscopy (AFM) confirm that the O₂-derived NiO films are smooth and that the quality of the epitaxy can be improved by decreasing the growth temperature and/or the precursor flow rate. However, low growth temperatures (400-500 °C) lead to rougher surfaces and carbon contamination. The H₂O-derived NiO films, which can be obtained only at relatively high temperatures (650-750 °C), exhibit slightly broader ω scan full width half-maximum (FWHM) values and rougher surfaces but no carbon contamination. Using H₂O as the oxidizer/protonolyzer, smooth and highly textured NiO (111) films can be grown on easily oxidized single crystal and highly textured Ni (200) metal substrates, which is impossible when O₂ is the oxidizer. The textural quality of these films depends on both the quality of the metal substrates and the gaseous precursor flow rate.