Highly tetrahedral hydrogenated amorphous carbon (ta-C:H) is deposited with a novel, 13.6 MHz excited electron cyclotron wave resonance (ECWR) plasma source. The ion flux of an acetylene and a nitrogen plasma was investigated by mass spectrometry and retarding field measurements. The ECWR gives a dissociation degree between 15&percent; and 80&percent; depending on gas flow rate. Ion current densities up to2 mA/cm2can be achieved, corresponding tota-C:H deposition rates of 2 nm/s. The fraction ofsp3bonded carbon atoms and mass density are strongly related to the amount of hydrogen in the ion flux. For low hydrogen ion fluxes (10&percent;), asp3fraction of 70&percent; and a mass density of2.85 g/cm3can be achieved. At higher hydrogen ion fluxes (40&percent;), thesp3fraction and the mass density fall to 55&percent; and2.55 gm/cm3,respectively. ©1998 American Institute of Physics.