Diamond-like carbon (DLC) films were synthesized on silicon substrates from solid carbon by a very low power (similar to 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 approximate to 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. (C) 2004 Kluwer Academic Publishers.