Chemical vapor deposition precursor chemistry. 3. Formation and characterization of crystalline nickel boride thin films from the cluster-assisted deposition of polyhedral borane compounds

Shreyas S. Kher, James T Spencer

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Abstract

The deposition of both metal-rich and boron-rich thin-film phases of nickel boride from boron-containing precursor compounds by a cluster deposition process is reported. The thin films were characterized by EDXA, AES, SEM, XRD, FT-IR, TEM, and electron diffraction experiments. The films were shown by AES to be compositionally uniform in the bulk sample. Film thicknesses up to 3 μm were readily prepared by controlling the flow rate of the borane into the cell, the substrate temperature, and the duration of the deposition. The stoichiometric composition of the films was controlled by regulating the deposition temperature, the borane flow rate into the reactor, and the base vacuum conditions during the film formation. A relationship was found to exist between the temperature during deposition and the film composition with a maximum nickel content reached at approximately 530°C. The effect of annealing both the nickel-rich and the boron-rich films was studied by SEM, XRD, and electron diffraction experiments. SEM data for the annealed boron-rich films showed the formation of perfect hexagonal crystals in a channelled columnar matrix. Electron diffraction data showed that this crystalline phase is hexagonal Ni7B3 isolated in a Ni3B matrix. The as-deposited nickel-rich films were found by XRD studies to be primarily pure nickel, containing relatively small amounts of the Ni3B phase relative to the pure nickel phase. This has been attributed to the precipitation of boron-rich phases as very small crystallites at the grain boundaries of the pure nickel material. XRD spectra for the boron-rich films showed that the films consisted of Ni3B with no pure nickel observed. Annealing of these films did not result in the formation of pure nickel phases in the XRD spectra.

Original languageEnglish (US)
Pages (from-to)538-544
Number of pages7
JournalChemistry of Materials
Volume4
Issue number3
StatePublished - 1992

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ASJC Scopus subject areas

  • Materials Science(all)
  • Materials Chemistry

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