Method and apparatus for providing flow-stabilized microdischarges in metal capillaries

摘要

Hollow cathode microdischarges in a tube geometry provides the formation of stable, high-pressure discharges in a variety of flowing gases including argon, helium, nitrogen, and hydrogen. Direct current discharges are ignited in stainless steel capillary tubes (dhole=178 mum) which are operated as the cathode and using a metal grid or plate as the anode. Argon discharges can be sustained at atmospheric pressure with voltages as low as 260 V for cathode-anode gaps of 0.5 mm. In one embodiment using a molybdenum substrate as the anode, microjets are struck in H2/CH4 mixtures at 200 Torr to deposit diamond films with well-faceted crystals. Optical emission spectroscopy of discharges used for growth confirms the presence of atomic hydrogen and CH radicals. Ballasting of individual tubes allows parallel operation of the microjets for larger area materials processing.