The Radio Frequency Hollow Cathode Discharge Induced by the RF Discharge in the Plasma-Jet Chemical Reactor (original) (raw)
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Ion current to a substrate in the pulsed dc hollow cathode plasma jet deposition system
Journal of Physics D: Applied Physics, 2010
The current of positive ions to a substrate was studied in the pulsed DC hollow cathode plasma jet system for deposition of thin films working at low pressures. Time evolution of electric current to a planar probe with pulsed negative DC bias was measured. The pulsing of the bias of the probe was applied to allow measurements with a dielectric film being deposited on its surface. The frequency of pulsing of the probe bias was higher than the frequency of pulsing of the discharge. Time evolution of the ion current density to the probe j i was determined for the whole period of modulation of the discharge for the discharge repetition frequency 2.5 kHz and different duty cycles D. The mean ion current density j i , averaged over the whole period of the discharge, was rising with the decreasing D although the value of the mean discharge current was kept constant. A simple theoretical model is proposed to explain this effect. It is shown that the observed rise of j i with decreasing D is in major part caused by the rise of the ion current in the afterglow region of the pulsed discharge.
Contributions to Plasma Physics, 2006
Low temperature low pressure hollow cathode plasma jet system working in static magnetic field was investigated by means of time resolved Langmuir probe technique. The hollow cathode discharge was excited in a cylindrical nozzle fabricated from Ti by continuous DC, pulsed DC, continuous wave radio-frequency (RF) and pulse-modulated RF power. Pure Ar was used as working gas. Electron distribution, electron density, and effective electron temperature were measured and compared between the different plasma jet excitation modes. Time evolution of plasma parameters was studied and compared with time evolution of power absorbed in the discharge in pulsed DC and pulse-modulated RF discharge excitation modes.
The Interaction of the Supersonic Plasma-Jet with the Substrate in the RF Plasma-Chemical Reactor
Contributions to Plasma Physics, 1996
Although the plasma-chemical processes and properties of the deposited thin film can strongly depend on the interaction of the supersonic plasma jet channel with the substrate, up to now the study of this phenomenon has not yet been done. We decided to study this interaction by means of CCD camera. The presented results indicate that the light intensity recorded close to the substrate can be used as a measure of the intensity of plasma-chemical deposition processes on the substrate surface.
IEEE Transactions on Plasma Science, 2013
High-density radio-frequency (RF) plasma sources have been produced by ring-shaped hollow-cathode discharge at various trench shapes. The influence of hollow-cathode trench shape on high-density plasma production has been investigated at a wide range of argon gas pressure and various input powers. The trench shapes are selected from well-typed, taper-typed, step-typed, and three improved step-typed trench shapes. It is revealed that, at the lower pressure less than 200 mtorr, the plasma density for the well-typed shape is the highest among the three shapes, while for the step-typed shape, it is the lowest. For the higher pressure more than 200 mtorr, the plasma density for the step-typed shape has the highest value. The results indicate that the plasma density for all typed shapes is almost proportional to RF input power. It is found that the improved step-typed trench shapes can attain a wide range of gas pressure sustaining higher plasma density. Index Terms-Capacitively coupled plasma, electron mean free path, high-density plasma source, ring-shaped hollow-cathode discharge, sheath thickness, step-typed trench, trench shape.
Hollow cathode and hybrid plasma processing
Vacuum, 2006
Generation and features of the radio frequency (rf) hollow cathode discharge (HCD) and its transition into the hollow cathode arc (HCA) are described. Rf linear hollow cathodes for generation of plasma over large areas and suitable for further scale-up are presented. Examples of surface processing and coating by PVD, both by HCD and HCA, are given. The hybrid reactor, combining hollow cathode and microwave plasmas, integrates features of both and provides more options to control plasma characteristics and consequently properties of deposited films. The rf hollow cathodes can be operated in both, PVD and PE CVD regimes, depending on process parameters. These regimes can even be combined within one process. New concepts of fused hollow cathode (FHC), microwave antenna (MWA) and Hybrid hollow electrode activated discharge (H-HEAD) cold atmospheric plasma sources are introduced. The FHC with its modular concept can be used for gas conversion, cleaning and for surface treatment of temperature-sensitive materials at ambient atmosphere. The H-HEAD cold atmospheric plasma source, capable of generating plasma plumes more than 15 cm long, enables treatment of 3-d and complex geometry objects even at low gas flows.
Characterization of a radio frequency hollow electrode discharge at low gas pressures
Physics of Plasmas, 2015
A radio frequency (RF) hollow discharge configuration is presented, which makes use of a combination of RF plasma generation and the hollow cathode effect. The system was especially designed for the treatment of nanoparticles, plasma polymerization, and nanocomposite fabrication. The process gas streams through the plasma in the inner of the cylindrical electrode system. In the here presented measurements, pure argon and argon with oxygen admixtures are exemplarily used. The discharge is characterized by probe measurements in the effluent, electrical measurements of the discharge parameters, and visual observations of the plasma glow. It is found that the RF fluctuations of the plasma potential are weak. The plasma potential resembles the one of a DC hollow cathode discharge, the RF hollow electrode acts as a cathode due to the self-bias, and a high voltage sheath forms in its inner cylinder. V C 2015 AIP Publishing LLC.
Plasma potential behavior and plume mode transitions in hollow cathode discharges
2007
Very large plasma potential oscillations in the plume of hollow cathode discharges were previously reported and correlated to the production of energetic ions in the neighborhood of the cathode exit. These energetic ions are likely the cause of keeper erosion issues observed in ion thrusters. The transition from the "quiescent" spot-mode to the "noisy" plume mode associated with high erosion rates was found to be a continuous increase in the plasma potential oscillation level as the gas flow was reduced or the current level increased. The large plasma potential oscillations are likely produced by turbulent ion acoustic waves, which are typically current driven and damped at low Mach numbers by Landau damping and by collisional effects, or by ionization instabilities generated in the hollow cathode discharge plasma near the cathode exit. It was found that injection of cold neutral gas directly into the cathode plume region near the keeper by an exterior gas feed could quench the oscillations and significantly reduce the number of high energy ions produced. This also greatly reduced the amount of gas required to be injected through the hollow cathode, which increases the plasma contact area with the emitting insert surface inside the cathode. These results indicate that energetic ion production and plume mode oscillations are due to instabilities in the cathode plume external to the hollow cathode.
The working principle of the hollow-anode plasma source
Plasma Sources Science and Technology, 1995
The hollow-anode discharge is a special form of glow discharge. It is shown that a drastically reduced anode area is responsible for a positive anode voltage drop of 30-40 V and an increased anode sheath thickness. This leads to an ignition of a relatively dense plasma in front of the anode hole. Langmuir probe measurements inside a specially designed hollow anode plasma source give an electron density and temperature of n e = 10 9 − 10 11 cm -3 and T e = 1 − 3 eV, respectively (nitrogen, current 100 mA, flow rate 5-50 scc/min). Driven by a pressure gradient, the "anode" plasma is blown through the anode hole and forms a bright plasma jet streaming with supersonic velocity (Mach number 1.2). The plasma stream can be used, for instance, in plasma-assisted deposition of thin films.