Method for forming amorphous carbon film

A method for forming an amorphous carbon film on a base material using an amorphous carbon film forming apparatus that includes a supporting electrode connected to ground and a counter electrode disposed so as to oppose the supporting electrode, comprising the steps of:

• (a) placing the base material on the supporting electrode, the base material being placed apart from the counter electrode;
• (b) establishing a pressure within the apparatus of 10 Torr or more and smaller than or equal to atmospheric pressure;
• and
• (c) forming an amorphous carbon film having a hardness of 2 GPa or more and 8 GPa or less by supplying a mixed gas of acetylene gas and a carrier gas carrying the acetylene gas between the supporting electrode and the counter electrode such that the percentage of the acetylene gas relative to the carrier gas is 0.05% by volume or more and 10% by volume or less, and by generating plasma while a DC pulse voltage having a pulse width of 0.1 μsec or more and 5.0 μsec or less is applied to the counter electrode.