Plasma pure carbon TVA discharges for hydrogen free carbon layer deposition

Presently there is a great interest in amorphous carbon (a-C) films that contain significant fractions of sp3 bonding. This bonding gives diamond like carbon (DLC) structures with many valuable properties, such as high mechanical hardness, low friction, transparency and chemical inertness. DLC can be prepared by a variety of vapor deposition techniques. A common feature is the growing from beams containing a significant fraction of medium energy ions (20 - 500 eV). There are two types of DLC: either unhydrogenated or hydrogenated. Thermionic Vacuum Arc can be used successfully for hydrogen free carbon film deposition, ensuring good qualities and high purity. Further developments are related mainly to the improvement of the TVA stability at the transition from electron bombardment heating of carbon rod to the TVA arc plasma heating. Additional heating of the carbon rod seems to be the best way to compensate heat loses and to ensure the needed stability. Preliminary tests of additional molybdenum reflector heating have confirmed our supposition that this is an efficient solution to compensate heat losses. Also, we observed during deposition experiments an activation process of the cathode, strong increase of the thermoelectronic current being observed. (authors)