Discharge behavior of C₂H₂ in mesh-cage shaped hollow cathode

The hydrogenated diamond-like carbon (DLC)coatings were synthesized by meshed plasma immersion ion deposition (MPIID) with acetylene(C₂H₂)as the carbon source. The impact of the growth conditions, including the ratios of C₂H₂ and Ar partial pressures and flow rates, pulsed voltage and working pressure, on the discharge behavior was investigated. The results show that the pulsed voltage, flow-rate and partial-pressure of C₂H₂ strongly affect the modes of pre-discharge and hollow cathode discharge. For example, as the C₂H₂ partial-pressure increased from 2.5 to 8 Pa, the breakdown voltage decreased from 1100 to 620 V;as the pulsed voltage of 900 V(at 200 mL/min of C₂H₂ flow-rate) increased to 1400 V(at 100 mL/min) the working pressure decreased by 1.4 and 3.9 Pa, respectively. An increase of the pulsed voltage and/or Ar partial-pressure increased the peak current, because of an increased hollow cathode discharge intensity. At a C₂H₂ and Ar partial-pressure ratio of 1:4, the highest current reached 32 A.