Spatial Distribution of Plasma Parameters in DC‐Energized Hollow Cathode Plasma Jet

Abstract

DC energized hollow cathode plasma jet system was examined by radially movable Langmuir probe. Radial distribution of electron concentration, plasma and floating potentials and mean electron energy were obtained from measured probe characteristics at the distance 17 mm downstream of the hollow cathode -nozzle. The radial dependence of plasma parameters was measured for distances from the system axis 0-120 mm in the discharge containing Ar and O2. Two scenarios were used: addition of O2 into the nozzle and into the plasma vessel. The differences in measured floating and plasma potential, electron density and mean electron energy radial courses obtained in the two scenarios are qualitatively explained. In addition temporal dependences of main plasma parameters for discharges in clean argon and argon-oxygen mixture were investigated that demonstrate system stability and its applicability for deposition of layers containing Ti. TiOx thin films were deposited onto glass substrates and examined by AFM and ellipsometry. It is illustrated that the differences in plasma parameters in the two scenarios of oxygen addition influence the layer properties.

Experimental Study of the Discharge in the Low Pressure Plasma Jet Sputtering System

“…Furthermore this research extends our previous work carried out under higher pressures reported in [17,18]. Furthermore this research extends our previous work carried out under higher pressures reported in [17,18].…”

“…Furthermore this research extends our previous work carried out under higher pressures reported in [17,18]. While as it was presented in [17] in the pressure range of tens of Pa the electron density decreases with the pressure due to faster recombination the dependence at low pressures seem to be inverse. From the measured Langmuir probe characteristics the floating and plasma potential, electron density, electron temperature and electron energy probability functions were evaluated.…”

“…In presented Langmuir probe measurements the attention was focused mainly on the situation when the plasma jet sputtering system was operated at low pressures around 1 Pa. As it was mentioned above such conditions have a big importance in the preparation of high crystallite surfaces. Furthermore this research extends our previous work carried out under higher pressures reported in [17,18]. All the experiments were performed at the discharge current of 300 mA when the delivered power attained the value of about 75 W. Movement of the Langmuir probe in the radial direction and movement of the plasma jet itself in the axial direction enabled to make a comprehensive image of the distribution of the plasma parameters within the whole active space in the reactor chamber.…”

“…Nevertheless as it is apparent from the picture the absolute values of the electron density are in the range of several Pa strongly dependent on the pressure. While as it was presented in [17] in the pressure range of tens of Pa the electron density decreases with the pressure due to faster recombination the dependence at low pressures seem to be inverse. It reveals that at lower pressures higher energetic particles are present in the reactor chamber volume and the ionization process takes place there.…”

Plasma parameters of RF capacitively coupled discharge: comparative study between a plane cathode and a large hole dimensions multi-hollow cathode

“…In such situation, the cathode geometry configuration is one of the possibilities that can improve the plasma parameters in terms of self-bias voltage (V dc ), electron density (n e ) and electron temperature (T e ), etc. [12][13][14]. In this sense, hollow and multi-hollow (H and MH) cathodes were proposed to be utilized as a light source [15], active media for gas lasers [16], sources of electrons [17], or for thin films deposition and large area surface treatment [18][19][20], and recently for the treatment of nanoparticles, plasma polymerization and nanocomposite fabrication [21].…”