Structural characterization of dual-metal containing diamond-like carbon nanocomposite films by pulsed laser deposition

Two metal dopants were simultaneously added into a diamond-like carbon (DLC) matrix using a KrF pulsed laser system at room temperature with no post-processing. The nanometer thin films were fabricated from carbon source targets containing the two metals of interest, Ti and Ni, in atomic percentages 2.5%, 5%, 7.5% and 10% each. Films from carbon targets containing only 5% Ni or 5% Ti were also deposited for comparison against the dual-metal containing films. Microstructure analysis shows that each individual metal reacted independently and uniquely with carbon as confirmed by XPS and surface analysis shows the presence of TiC bonds and Ni⁰. Therefore, there was no reaction between Ti and Ni as metals confirmed by XPS. Through this independent interaction, a superposition of microstructural properties was obtained as if the metals were doped separately into DLC. The separate interactions of the two metals with carbon were important as they were able to play separate and different roles in enhancing the properties of DLC. In addition, TEM analysis confirmed a unique self-assembly state where the nickel ions converge into nanosized clusters of ～ 5 nm in diameter and predominantly oriented in a (200) direction. The resultant films were also extremely smooth with RMS roughness of about 0.1 nm, thus retaining the inherent smoothness of DLC films. The combined Ti/Ni films could be used as substrates to grow carbon nanotubes with controlled density which could be used as cold electron emitters. Thus, it is interesting to study the growth mechanism and microstructure of the composite films.