A dual-cathode arc plasma source is combined with a computer-controlled bias amplifier to synchronize substrate bias with the pulsed production of plasma. Accordingly, bias can be applied in a material-selective way. The principle has been applied to the synthesis metal-doped diamond-like carbon films, where the bias was applied and adjusted when the carbon plasma was condensing, and the substrate was at ground when the metal was incorporated. In doing so, excessive sputtering by too-energetic metal ions can be avoided while the sp.sup.3/sp.sup.2 ratio can be adjusted. It is shown that the resistivity of the film can be tuned by this species-selective bias. The principle can be extended to multiple-material plasma sources and complex materials.
 This invention was made with government support under Contract No. DE-AC03-76SF00098/DE-AC02-05CH11231 awarded by the U.S. Department of Energy. The government has certain rights in the invention.