confirmed that in the above process sulfur atoms promote the formation of the carbon fibers by unknown mechanism as the reaction proceeds the solution 3 as a source material is consumed but the consumed solution is supplied using the solution 8 in the glass reaction vessel 7 to keep the liquid level always constant the carbon fibers produced in such a method have an amorphous structure because the growth temperature is as low as 300 to 700 u00b0 c in addition because the carbon fibers are produced in the saturated vapor of the solution the surface of the carbon fibers absorb substances originating from the solution this provides the advantage that the carbon fibers are not oxidized and kept stably and the surface activity thereof is maintained to improve the compatibility with a resin material as the material of the substrate platinum pt rhodium rh ruthenium ru nickel ni iron fe titanium ti palladium pd copper cu aluminum al tungsten w silicon si molybdenum mo cobalt co yttrium y or an alloy of at least two of these metals may be used with ni being most preferable in addition it was found as a result of investigations that when a sulfur compound was incorporated into the metal substrate by for example heating in a sulfur vapor or surface treatment.