Pavel Baroch

Discharge in dual magnetron sputtering system

A dual magnetron sputtering system represents a very effective tool, particularly for reactive magnetron sputtering of insulated thin films. For an efficient deposition process, however, it is very important to optimize the electrical and magnetic field of the magnetron. Images of plasma discharges in different magnetic field configurations of the dual magnetron are presented.

Special type of plasma dielectric barrier discharge reactor for direct ozonization of water and degradation of organic pollution

A system based on the dielectric barrier discharge (DBD) with improved discharge homogeneity, used for direct ozonization and purification of water, is presented here. A special design of the atmospheric DBD system is characterized by incorporation of a porous ceramic segment in the zone between electrodes. This porous segment was placed on the metallic electrode and served as a guide for flowing water. Due to the hydrophilic force it allowed the water to remain undisturbed by the electrical discharge. This feature enabled a reduction of the discharge gap and subsequently an increase in the intensity, stability and homogeneity of the discharge. It was observed that under such a configuration a transition from the filamentary mode to the semi-homogeneous mode of the plasma discharge could be realized. Discharge properties were investigated by the optical emission spectroscopy method and the results showed the domination of nitrogen lines in the UV-A region. Further it was observed that the system can be operated in a wide range of liquid conductivities and under negligible heat deposition to the liquid solution. Finally, the formation of dissolved ozone and hydrogen peroxide in the deionized water was measured and decomposition tests with organic dye were performed.

Two-Functional Direct Current Sputtered Silver-Containing Titanium Dioxide Thin Films

The article reports on structure, mechanical, optical, photocatalytic and biocidal properties of Ti–Ag–O films. The Ti–Ag–O films were reactively sputter-deposited from a composed Ti/Ag target at different partial pressures of oxygen on unheated glass substrate held on floating potentialUfl. It was found that addition of ~2 at.% of Ag into TiO2film has no negative influence on UV-induced hydrophilicity of TiO2film. Thick (~1,500 nm) TiO2/Ag films containing (200) anatase phase exhibit the best hydrophilicity with water droplet contact angle (WDCA) lower than 10° after UV irradiation for 20 min. Thick (~1,500 nm) TiO2/Ag films exhibited a better UV-induced hydrophilicity compared to that of thinner (~700 nm) TiO2/Ag films. Further it was found that hydrophilic TiO2/Ag films exhibit a strong biocidal effect under both the visible light and the UV irradiation with 100% killing efficiency ofEscherichia coli ATCC 10536 after UV irradiation for 20 min. Reported results show that single layer of TiO2with Ag distributed in its whole volume exhibits, after UV irradiation, simultaneously two functions: (1) excellent hydrophilicity with WDCA < 10° and (2) strong power to killE. coli even under visible light due to direct toxicity of Ag.

Plasma Drift in Dual Magnetron Discharge

The distribution and form of the discharge in dual magnetron (DM) depends not only on the polarity of magnets used in both magnetrons but also on the distribution of magnetic field lines. For tilted DM, a naturally created gradient of magnetic field generates a drift of plasma that results in a deflection of the discharge from the plane of symmetry. This deflection of the discharge was observed experimentally. Performed experiments are in a good agreement with the theoretical prediction.

Magnetron with gas injection through hollow cathodes machined in sputtered target

Abstract This article reports on a magnetron equipped with a target with holes. The holes machined in sputtered target can sustain hollow cathode discharges and/or inject the sputtering gas directly inside the magnetron discharge. This magnetron operates on the same principle as a gas-jet. It is shown that the size and number of holes can efficiently control I – V characteristics of the magnetron. The holes of large (≥2 mm) diameter can sustain hollow cathode discharges, which intensify the magnetron discharge. On the contrary, the holes of small (≤1 mm) diameter influences the I – V characteristics much less and allow: (i) to introduce the sputtering gas directly inside the discharge; and (ii) to compensate a gas density reduction in front of target when the magnetron is operated at high (≥100 W/cm 2 ) target power densities. Special attention is devoted to reactive sputtering. There is great difference in the deposition rate a D of films in the case when the sputtering gas is fed to the chamber or to the discharge through the holes. It is shown that for the gas feed to chamber, a D of the nitride films, sputtered from target with four holes of diameter 2 mm, is equal to that of pure metal films sputtered from a full target in argon. On the contrary, for the gas feed to discharge, a D of the oxide films, sputtered from target with four holes of diameter 2 mm, is very low, 40 times smaller compared to a D of metal films sputtered from a full target in argon. The magnetron discharge with an extremely low deposition rate is very suitable for cleaning and activation of surfaces prior to the film deposition.

Rapid Sterilization of Escherichia coli by Solution Plasma Process

Solution plasma (SP), which is a discharge in the liquid phase, has the potential for rapid sterilization of water without chemical agents. The discharge showed a strong sterilization performance against Escherichia coli bacteria. The decimal value (D value) of the reduction time for E. coli by this system with an electrode distance of 1.0 mm was estimated to be approximately 1.0 min. Our discharge system in the liquid phase caused no physical damage to the E. coli and only a small increase in the temperature of the aqueous solution. The UV light generated by the discharge was an important factor in the sterilization of E. coli.

Bipolar Pulsed Electrical Discharges in Liquid

Electrical discharges in water offer a unique plasma source which can be utilized in various novel applications. These discharges are distinguished for the rapid in situ production of highly reactive species when high voltage of about 10-20 kV is applied. Images of the plasma discharges in the water, which are generated by using high-frequency bipolar pulse power supply at relatively low ignition voltages, are presented here.

Generation of plasmas in water: utilization of a high-frequency, low-voltage bipolar pulse power supply with impedance control

Presented work focuses on the investigation and characterization of plasma discharges generated in water by newly developed bipolar pulse power supply. The main aim of our work was to solve and overcome problems with intensive arc discharge transition when the discharge is ignited and maintained by a low output impedance pulse power supply. For this purpose a novel type of bipolar pulse power supply was developed and tested. It was found that two distinguished stable modes of discharges generated in the water can be realized. Effects of water conductivity, pulse frequency and initial water temperature on the discharge properties were investigated. Optical emission spectroscopy was employed to study plasma parameters of the discharge and the correlation between the data obtained from the optical emission spectroscopy and the chemical species measured in the water was carried out.

Degradation of Bacteria Using Pulse Plasma Discharge in Liquid Medium

The paper reports on the study of an underwater electrical pulse plasma discharge operating under relatively low discharge voltages (below 1 kV) and its utilization for degradation of bacteria contained in the liquid medium. For this purpose, a system based on wire-to-wire electrode configuration was designed. Results show the ability of the system to generate active species, observed by optical emission spectroscopy and also revealed from the change in pH of treated solution. Effective generation of these species then results in a relatively fast decomposition rate of tested organic dyes. Consequent treatment process with two types of bacteria also exhibits positive results showing successful and very fast decrease in bacteria population