NOVELTY - An electroconductive base material is dipped into methane gas plasma. The radicals of plasma are deposited on base material surface. The positive ions or electrons are then accelerated. Base material is irradiated using positive ions of plasma by negative voltage application or electrons of plasma by positive pulse application, and an ion implantation layer is formed at surface of base material to form carbonitride film.    USE - For forming amorphous carbonitride film used for manufacturing highly conductive amorphous carbonitride film base material composite used for electrode or highly conductive components such as switch contacts and separator for fuel cells (all claimed).    ADVANTAGE - The method enables the formation of amorphous carbonitride film having excellent electroconductivity, corrosion resistance and adhesion. The amorphous carbonitride film is manufactured at low temperature.    DETAILED DESCRIPTION - An electroconductive base material is dipped into methane gas plasma in a vacuum chamber. The radicals of plasma are deposited on base material surface. The positive ions or electrons are then accelerated. The base material is irradiated using positive ions or electrons of plasma, and an ion implantation layer is formed at the surface of base material to form amorphous carbonitride film. The base material is irradiated using positive ions, when negative voltage is applied, and the base material is irradiated using electrons, when positive pulse is applied. The methane gas plasma is obtained by introducing a mixed gas of hydrocarbon and nitrogen into the vacuum chamber.    INDEPENDENT CLAIMS are included for the following:    (1) manufacture of highly conductive amorphous carbonitride film base material composite;    (2) highly conductive amorphous carbonitride film base material composite; and    (3) electrode or highly conductive component.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic view of amorphous carbonitride film forming apparatus. (Drawing includes non-English language text).