Abstract: A method of producing layers of hard carbon modifications on a substrate includes disposing the substrate in a vacuum chamber in which an anode electrode and a cathode electrode are disposed and spaced from one another. The anode electrode is made of a carbon containing material and serves as a carbon source when a direct current is formed between the spaced electrodes. The two electrodes are energized, thereby forming a direct current arc in the vacuum between the spaced electrodes; and hydrogen is introduced directly into the region of the arc by flowing hydrogen through at least one of the two electrodes while simultaneously maintaining the arc between the electrodes to feed the arc with carbon from the anode thereby coating a surface of the substrate with a hard carbon layer.