Synthesis of HDLC films from solid carbon

• Published in: Journal of materials science 2004-05, Vol.39 (10), p.3309-3318
• Main Authors: Mills, R. L, Sankar, J, Ray, P, Voigt, A, He, J, Dhandapani, B
• Format: Article
• Language: English
• Subjects: Bombardment; Carbon; Catalysis; catalysts; catalytic activity; Chemical vapor deposition; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Coatings; Cross-disciplinary physics: materials science; rheology; Diamond-like carbon films; Etching; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Helium; Hydrides; Hydrogen; Hydrogen plasma; mass spectrometry; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Microwave plasmas; Organic chemistry; Photoelectrons; Physics; Plasma etching; protons; Raman spectroscopy; Secondary ion mass spectroscopy; silicon; Silicon substrates; Specific materials; Spectrum analysis; Stabilization; temperature; Time of flight photoelectron coincidence spectroscopy; vapors; X ray photoelectron spectroscopy
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1023/B:JMSC.0000026931.98685.59

Diamond-like carbon (DLC) films were synthesized on silicon substrates from solid carbon by a very low power (∼60 W) microwave plasma chemical vapor deposition (MPCVD) reaction of a mixture of 90–70% helium and 10–30% hydrogen. It is proposed that He⁺ served as a catalyst with atomic hydrogen to form an energetic plasma. The average hydrogen atom temperature of a helium-hydrogen plasma was measured to be up to 180–210 eV versus ≈3 eV for pure hydrogen. Bombardment of the carbon surface by highly energetic hydrogen formed by the catalysis reaction may play a role in the formation of DLC. The films were characterized by time of flight secondary ion mass spectroscopy (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. TOF-SIMS identified the coatings as hydride by the large H⁺ peak in the positive spectrum and the dominant H⁻ in the negative spectrum. The XPS identification of the H content of the CH coatings as a novel hydride corresponding to a peak at 49 eV has implications that the mechanism of the DLC formation may also involve one or both of selective etching of graphitic carbon and the stabilization of sp ³-bonded carbon by the hydrogen catalysis product. Thus, a novel H intermediate formed by the plasma catalysis reaction may enhance the stabilization and etching role of H used in past methods.