Tailoring the Properties of Atomic Layer Deposited Nickel and Nickel Carbide Thin Films via Chain-Length Control of the Alcohol Reducing Agents

Abstract

Atomic layer deposition (ALD) of nickel and nickel carbide is reported starting from nickel acetylacetonate and a primary alcohol. The sequential reactions of both reactants with the adsorbed species are shown to be self-limited. Use of propanol or ethanol as reducing agents yields the formation of the technologically relevant carbon-Ni3C thin films, whereas the carbon content with use of methanol is less than 5 atom %. These metallic nickel thin films are electrically conductive and feature a soft ferromagnetic behavior. The thermally stable cubic lattice of nickel was grown at 300 °C with methanol as a reducing agent while the metastable hexagonal structure was obtained at lower temperatures. The morphology and the structure of the films were investigated with use of scanning electron microscopy and X-ray diffraction. The films are nanocrystalline featuring an average crystallite size of ∼10 nm. Hydrogen-free ALD of nickel is particularly appealing for the deposition of (i) conformal coatings on hydrogen-sensitive substrates such as highly reducible oxides and metals with high capacity to form hydrides and (ii) 3D nanomaterials with high aspect ratio.