A cylindrical hollow cathode discharge(HCD) in CH4 /Ar gas mixture at pressure of 20-30 Pa was used to deposit diamond-like carbon(DLC) films on the inner surface of a stainless steel tube. The characteristics of the HCD including the voltage-current curves, the plasma images and the optical emission spectrum(OES) were measured in Ar and CH4 /Ar mixtures. The properties of DLC films prepared under di?erent conditions were analyzed by means of Raman spectroscopy and scanning electron microscopy(SEM). The results show that the electron excitation temperature of HCD plasma is about 2400 K. DLC films can be deposited on the inner surface of tubes. The ratio of sp3/sp2bonds decreases with the applied voltage and the deposition time. The optimizing CH4 content was found to be around CH4 /Ar =1/5 for good quality of DLC films in the present system.
In this study, micro-hollow cathode discharge (MHCD) is investigated by a fluid model with drift-diffusion approximation. The MHC device is a cathode/dielectric/anode sandwich structure with one hole of a diameter D=200 μm. The gas is a Ne/Xe mixture at a pressure p=50～500 Torr. The evolutions of the discharge show that there are two different discharge modes. At larger pD the discharge plasma and high density excited species expand along the cathode surface and, a ringed discharge mode is formed. At smaller pD, the discharge plasma and the excited species expand along the axis of the cathode aperture to form a columnar discharge.
HE FengHE ShoujieZHAO XiaofeiGUO BingangOUYANG Jiting
The microwave(MW) transmission method is employed to measure both the plasma density and the plasma decay time in the hollow cathode discharge(HCD) in argon at low pressure. The plasma density in DC-driven or pulsed HCD is on the order of 1012cm 3, which can block the X-band MW effectively. In the case of pulsed HCD, the MW transmittance shows the same waveform as the pulsed current during the rising edge if the driving frequency is low, but with a longer delay during the falling edge. The MW transmittance reaches a constant low level when the driving frequency is high enough. The plasma decay time in the HCD system is measured to be about 100 μs around a pressure of 120 Pa. The ambipolar diffusion is considered to be the major mechanism in the decay process.
