Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018)
    Thin Films Tuesday Sessions
       Session TF-TuE

Paper TF-TuE8
Diamond-like Carbon Thin Film Deposition using Low-energy Ion Beams

Tuesday, December 4, 2018, 8:00 pm, Room Naupaka Salons 4

Session: Next-generation Protective Coatings and Tribological Applications
Presenter: Magdaleno, Jr. Vasquez, University of the Philippines
Authors: A.G. Cuevas, University of the Philippines
M.G.K. Ramos, University of the Philippines
A.V. Catapang, University of the Philippines
M.R. Vasquez, University of the Philippines
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Diamond-like carbon (DLC) is a metastable form of carbon that has characteristics similar to diamond. High hardness, low wear rate, and chemically inert are some desirable properties of DLC that find a host of industrial applications. Diamond-like properties are greatly dictated by sp2/sp3 ratio of hybridized carbon and hydrogen atoms that are present in the DLC matrix. High sp3 content in DLC can be achieved when carbon ion energy incident on a substrate is in the range of 100 eV. In this work, we developed a two-electrode ion source system capable of extracting broad ion beams with mean ion energies around 100 eV. The ion reservoir is made of stainless steel with permanent magnets around the cylindrical body to realize a multicusp configuration. Quiescent plasma was produced using 0.3 mm dia tungsten wires as hot cathodes. Acetylene (C2H2) was used as the carbon source with argon (Ar) as background gas. Doping was also done by introducing nitrogen (N2) gas into the system. Retarding potential analyzer measurements suggest the successful generation of tunable broad ion beams with mean energies around 100 eV and current densities of around 10-6 A/cm2. The dissociation of Ar/C2H2 and Ar/C2H2/N2 plasma were obtained using a residual gas analyzer. The mass spectra of the Ar/C2H2 ion beam showed the presence of mostly hydrocarbon radicals such as C2H2+, C2H+, CH+, as well as heavier CXHY+ radicals and monatomic carbon and Ar. For Ar/C2H2/N2 ion beam, CN radicals, monatomic and diatomic N were also observed. Compositional analyses of the films via Raman spectroscopy revealed the successful growth of DLC with sp3 content of up to 80%. Energy-dispersive x-ray spectroscopy measurements show up to 10\% doping implying the successful and uniform incorporation of N in the DLC matrix. Improvement in adhesion was also observed for N-doped DLC films. X-ray photoelectron spectral measurements suggest the presence of sp2 and sp3 on the surface which supports the subplantation growth scheme of DLC. X-ray diffractometry suggests the presence of diamond and graphite phases in a generally amorphous films . Surface analyses employed using scanning electron microscopy showed good conformity of the DLC films with increasing thickness upon the subsequent increase in C2H2 content. Hardness testing via nanoindentation show acceptable hardness values of around 8 GPa. These films may find applications in tribological coatings.