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Johanna Rosen - One of the best experts on this subject based on the ideXlab platform.
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effect of mo cu Cathode composition on process stability macroparticle formation plasma generation and thin film deposition in dc arc synthesis
Journal of Applied Physics, 2020Co-Authors: Igor Zhirkov, Peter Polcik, Andrejs Petruhins, Szilard Kolozsvári, Johanna RosenAbstract:In this work, we present the correlation between Cathode composition and features of the arcing process for Mo1 − xCux [x = 0.0, 0.07 (0.05), 0.14 (0.10), 0.21 (0.15), 0.40 (0.3), 0.73 (0.63), 0.97 (0.95), and 1.00, atomic fraction (weight fraction)] Cathodes used in a DC vacuum-arc deposition system. It is found that the stability of the arcing process crucially depends on the Cathode composition. The most stable arc spot and the lowest Cathode potential (∼19 V) are detected for the Mo0.27Cu0.73 Cathode, while the Mo0.93Cu0.07 Cathode shows the most unstable arcing process with the highest Cathode potential (∼28 V). The properties of the generated plasma are also strongly dependent on the relative ratio of the Cathode elements. The metal ions from the Mo and Cu Cathodes have peak kinetic energies around 136 and 62 eV, respectively, while for a Mo0.79Cu0.21 Cathode, the corresponding energies are only 45 and 28 eV. The average charge states decreased from 2.1 to 1.6 for Mo ions and from 2 to 1.2 for Cu ions. The intensity of macroparticle generation and the size of the droplets correlate with the relative fraction of Cu. However, it is shown that, typically for the Cathodes with a low amount of Cu, an increased abundance of visually observed macroparticles leads to droplet-free films. The film thicknesses and their compositions also demonstrate dependencies on the elemental composition of the Cathode. These results are discussed in the light of no solubility between Mo and Cu and the high temperature of the Cathode surface during the arcing process.
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Effect of Ti-Al Cathode grain size on plasma generation and thin film synthesis from a direct current vacuum arc plasma source
AIP Publishing LLC, 2019Co-Authors: Igor Zhirkov, Peter Polcik, Andrejs Petruhins, Szilard Kolozsvári, Johanna RosenAbstract:Herein, we investigate the influence of powder metallurgical manufactured Ti0.5Al0.5 Cathode grain size (45-150 μm) on the properties of a DC arc discharge, for N2 pressures in the range 10-5 Torr (base pressure) up to 3x10-2 Torr. Intermetallic TiAl Cathodes are also studied. The arc plasma is characterized with respect to ion composition, ion charge state, and ion energy, and is found to change with pressure, independent on choice of Cathode. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the Cathode surfaces and the concurrently deposited films are used for exploring the correlation between Cathode-, plasma-, and film composition. The plasma has a dominating Al ion content at elevated pressures, while the film composition is consistent with the Cathode composition, independent on Cathode grain size. Cross-sections of the used Cathodes are studied, and presence of a converted layer, up to 10 μm, is shown, with an improved intermixing of the elements on the Cathode surface. This layer is primarily explained by condensation of Cathode material from the melting and splashes accompanying the arc spot movement, as well as generated plasma ions being redeposited upon returning to the Cathode. The overall lack of dependence on grain size is likely due to similar physical properties of Ti, Al and TiAl grains, as well as the formation of a converted layer. The presented findings are of importance for large scale manufacturing and usage of Ti-Al Cathodes in industrial processes
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effect of ti al Cathode composition on plasma generation and plasma transport in direct current vacuum arc
Journal of Applied Physics, 2014Co-Authors: Igor Zhirkov, Andrejs Petruhins, Anders Eriksson, Martin Dahlqvist, Arni Sigurdur Ingason, Johanna RosenAbstract:DC arc plasma from Ti, Al, and Ti1-xAlx (x = 0.16, 0.25, 0.50, and 0.70) compound Cathodes was characterized with respect to plasma chemistry and charge-state-resolved ion energy. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the deposited films and the Cathode surfaces were used for exploring the correlation between Cathode-, plasma-, and film composition. Experimental work was performed at a base pressure of 10−6 Torr, to exclude plasma-gas interaction. The plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the Cathode composition, while deposited films were in accordance with the Cathode stoichiometry. This may be explained by presence of neutrals in the plasma/vapour phase. The average ion charge states (Ti = 2.2, Al = 1.65) were consistent with reference data for elemental Cathodes, and approximately independent on the Cathode composition. On the contrary, the width of the ion energy distributions (IEDs) were drastically...
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characterization of plasma chemistry and ion energy in cathodic arc plasma from ti si Cathodes of different compositions
Journal of Applied Physics, 2013Co-Authors: Anders Eriksson, Igor Zhirkov, Martin Dahlqvist, Jens Jensen, Lars Hultman, Johanna RosenAbstract:Arc plasma from Ti-Si compound Cathodes with up to 25 at. % Si was characterized in a DC arc system with respect to chemistry and charge-state-resolved ion energy. The plasma ion composition showed a lower Si content, diverging up to 12 at. % compared to the Cathode composition, yet concurrently deposited films were in accordance with the Cathode stoichiometry. Significant contribution to film growth from neutrals is inferred besides ions, since the contribution from macroparticles, estimated by scanning electron microscopy, cannot alone account for the compositional difference between Cathode, plasma, and film. The average ion charge states for Ti and Si were higher than reference data for elemental Cathodes. This result is likely related to TiSix phases of higher cohesive energies in the compound Cathodes and higher effective electron temperature in plasma formation. The ion energy distributions extended up to ∼200 and ∼130 eV for Ti and Si, respectively, with corresponding average energies of ∼60 and ∼30 eV. These averages were, however, not dependent on Si content in the Cathode, except for 25 at. % Si where the average energies were increased up to 72 eV for Ti and 47 eV for Si.
Bruce E. Logan - One of the best experts on this subject based on the ideXlab platform.
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impact of cleaning procedures on restoring Cathode performance for microbial fuel cells treating domestic wastewater
Bioresource Technology, 2019Co-Authors: Ruggero Rossi, Wulin Yang, Xu Wang, Bruce E. LoganAbstract:Abstract Degradation of Cathode performance over time is one of the major drawbacks in applications of microbial fuel cells (MFCs) for wastewater treatment. Over a two month period the resistance of air Cathodes (RCt) with a polyvinylidene fluoride (PVDF) diffusion layer increased of 111% from 70 ± 10 mΩ m2 to 148 ± 32 mΩ m2. Soaking the Cathodes in hydrochloric acid (100 mM HCl) restored Cathode performance to RCt = 74 ± 17 mΩ m2. Steam, ethanol, or sodium hydroxide treatment produced only a small change in performance, and slightly increased RCt. With a polytetrafluoroethylene (PTFE) diffusion layer on the Cathodes, RCt increased from 54 ± 14 mΩ m2 to 342 ± 142 mΩ m2 after two months of operation. The acid concentration was critical for effectiveness in cleaning, as HCl (100 mM) decreased RCt to 28 ± 8 mΩ m2. A lower concentration of HCl (
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engineering a membrane based air Cathode for microbial fuel cells via hot pressing and using multi catalyst layer stacking
Environmental Science: Water Research & Technology, 2016Co-Authors: Wulin Yang, Bruce E. LoganAbstract:Microbial fuel cell (MFC) Cathodes must have high performance and be resistant to water leakage. Hydrophobic poly(vinylidene fluoride) (PVDF) membranes have shown great advantages in providing a waterproof diffusion layer for MFCs and reducing the Cathode costs. However, previous approaches have lacked a method to integrate the diffusion layer into the Cathode structure. Here, a hot pressing was used to bind the PVDF diffusion layer onto the air side of the activated carbon Cathode, and additional catalyst layers were added to improve performance. Cathodes pressed at 60 °C produced a 16% higher maximum power density of 1630 ± 10 mW m−2 than non-pressed controls (1400 ± 7 mW m−2). Cathode performance was further increased to 1850 ± 90 mW m−2 by catalyst stacking, through the addition of an extra catalyst layer (CL), which better utilized the available surface area of the stainless steel mesh (SS) current collector. The use of one stainless steel current collector and two catalyst layers (SS/2CLs) produced more positive Cathode potentials compared to other designs (SS/CL or 2SS/2CL). Low material costs and high power production for MFCs using these Cathodes could enable more cost effective power production using MFCs.
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diffusion layer characteristics for increasing the performance of activated carbon air Cathodes in microbial fuel cells
Environmental Science: Water Research & Technology, 2016Co-Authors: Xia Huang, Peng Liang, Wulin Yang, Xiaoyuan Zhang, Jia Liu, Qiuying Wang, Bruce E. LoganAbstract:The characteristics of several different types of diffusion layers were systematically examined to improve the performance of activated carbon air Cathodes used in microbial fuel cells (MFCs). A diffusion layer of carbon black and polytetrafluoroethylene (CB + PTFE) that was pressed onto a stainless steel mesh current collector achieved the highest Cathode performance. This Cathode also had a high oxygen mass transfer coefficient and high water pressure tolerance (>2 m), and it had the highest current densities in abiotic chronoamperometry tests compared to Cathodes with other diffusion layers. In MFC tests, this Cathode also produced maximum power densities (1610 ± 90 mW m−2) that were greater than those of Cathodes with other diffusion layers, by 19% compared to Gore-Tex (1350 ± 20 mW m−2), 22% for a cloth wipe with PDMS (1320 ± 70 mW m−2), 45% with plain PTFE (1110 ± 20 mW m−2), and 19% higher than those of Cathodes made with a Pt catalyst and a PTFE diffusion layer (1350 ± 50 mW m−2). The highly porous diffusion layer structure of the CB + PTFE had a relatively high oxygen mass transfer coefficient (1.07 × 10−3 cm s−1) which enhanced oxygen transport to the catalyst. The addition of CB enhanced Cathode performance by increasing the conductivity of the diffusion layer. Oxygen mass transfer coefficient, water pressure tolerance, and the addition of conductive particles were therefore critical features for achieving higher performance AC air Cathodes.
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Pressurized air Cathodes for enhanced stability and power generation by microbial fuel cells
Journal of Power Sources, 2016Co-Authors: Wulin Yang, Jia Liu, Yushi Tian, Xiuping Zhu, Yujie Feng, Bruce E. LoganAbstract:Abstract Large differences between the water and air pressure in microbial fuel cells (MFCs) can deform and damage Cathodes. To avoid deformation, the Cathode air pressure was controlled to balance pressure differences between the air and water. Raising the air pressures from 0 to 10 kPa at a set Cathode potential of −0.3 V (versus Ag/AgCl) enhanced Cathode performance by 17%, but pressures ≥25 kPa decreased current and resulted in air leakage into the solution. Matching the air pressure with the water pressure avoided Cathode deformation and improved performance. The maximum power density increased by 15%, from 1070 ± 20 to 1230 ± 70 mW m −2 , with balanced air and water pressures of 10–25 kPa. Oxygen partial pressures ≥12.5 kPa in the Cathode compartment maintained the oxygen reduction rate to be within 92 ± 1% of that in ambient air. The use of pressurized air flow through the Cathode compartments can enable closer spacing of the Cathodes compared to passive gas transfer systems, which could make the reactor design more compact. The energy cost of pressurizing the Cathodes was estimated to be smaller than the increase in power that resulted from the use of pressurized Cathodes.
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single step fabrication using a phase inversion method of poly vinylidene fluoride pvdf activated carbon air Cathodes for microbial fuel cells
Environmental Science and Technology Letters, 2014Co-Authors: Wulin Yang, Fang Zhang, Michael A. Hickner, Bruce E. LoganAbstract:Air Cathodes used in microbial fuel cells (MFCs) need to have high catalytic activity for oxygen reduction, but they must also be easy to manufacture, inexpensive, and watertight. A simple one-step, phase inversion process was used here to construct an inexpensive MFC Cathode using a poly(vinylidene fluoride) (PVDF) binder and an activated carbon catalyst. The phase inversion process enabled Cathode preparation at room temperatures, without the need for additional heat treatment, and it produced for the first time a Cathode that did not require a separate diffusion layer to prevent water leakage. MFCs using this new type of Cathode produced a maximum power density of 1470 ± 50 mW m–2 with acetate as a substrate, and 230 ± 10 mW m–2 with domestic wastewater. These power densities were similar to those obtained using Cathodes made using more expensive materials or more complex procedures, such as Cathodes with a polytetrafluoroethylene (PTFE) binder and a poly(dimethylsiloxane) (PDMS) diffusion layer, or a ...
Igor Zhirkov - One of the best experts on this subject based on the ideXlab platform.
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effect of mo cu Cathode composition on process stability macroparticle formation plasma generation and thin film deposition in dc arc synthesis
Journal of Applied Physics, 2020Co-Authors: Igor Zhirkov, Peter Polcik, Andrejs Petruhins, Szilard Kolozsvári, Johanna RosenAbstract:In this work, we present the correlation between Cathode composition and features of the arcing process for Mo1 − xCux [x = 0.0, 0.07 (0.05), 0.14 (0.10), 0.21 (0.15), 0.40 (0.3), 0.73 (0.63), 0.97 (0.95), and 1.00, atomic fraction (weight fraction)] Cathodes used in a DC vacuum-arc deposition system. It is found that the stability of the arcing process crucially depends on the Cathode composition. The most stable arc spot and the lowest Cathode potential (∼19 V) are detected for the Mo0.27Cu0.73 Cathode, while the Mo0.93Cu0.07 Cathode shows the most unstable arcing process with the highest Cathode potential (∼28 V). The properties of the generated plasma are also strongly dependent on the relative ratio of the Cathode elements. The metal ions from the Mo and Cu Cathodes have peak kinetic energies around 136 and 62 eV, respectively, while for a Mo0.79Cu0.21 Cathode, the corresponding energies are only 45 and 28 eV. The average charge states decreased from 2.1 to 1.6 for Mo ions and from 2 to 1.2 for Cu ions. The intensity of macroparticle generation and the size of the droplets correlate with the relative fraction of Cu. However, it is shown that, typically for the Cathodes with a low amount of Cu, an increased abundance of visually observed macroparticles leads to droplet-free films. The film thicknesses and their compositions also demonstrate dependencies on the elemental composition of the Cathode. These results are discussed in the light of no solubility between Mo and Cu and the high temperature of the Cathode surface during the arcing process.
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Effect of Ti-Al Cathode grain size on plasma generation and thin film synthesis from a direct current vacuum arc plasma source
AIP Publishing LLC, 2019Co-Authors: Igor Zhirkov, Peter Polcik, Andrejs Petruhins, Szilard Kolozsvári, Johanna RosenAbstract:Herein, we investigate the influence of powder metallurgical manufactured Ti0.5Al0.5 Cathode grain size (45-150 μm) on the properties of a DC arc discharge, for N2 pressures in the range 10-5 Torr (base pressure) up to 3x10-2 Torr. Intermetallic TiAl Cathodes are also studied. The arc plasma is characterized with respect to ion composition, ion charge state, and ion energy, and is found to change with pressure, independent on choice of Cathode. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the Cathode surfaces and the concurrently deposited films are used for exploring the correlation between Cathode-, plasma-, and film composition. The plasma has a dominating Al ion content at elevated pressures, while the film composition is consistent with the Cathode composition, independent on Cathode grain size. Cross-sections of the used Cathodes are studied, and presence of a converted layer, up to 10 μm, is shown, with an improved intermixing of the elements on the Cathode surface. This layer is primarily explained by condensation of Cathode material from the melting and splashes accompanying the arc spot movement, as well as generated plasma ions being redeposited upon returning to the Cathode. The overall lack of dependence on grain size is likely due to similar physical properties of Ti, Al and TiAl grains, as well as the formation of a converted layer. The presented findings are of importance for large scale manufacturing and usage of Ti-Al Cathodes in industrial processes
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effect of ti al Cathode composition on plasma generation and plasma transport in direct current vacuum arc
Journal of Applied Physics, 2014Co-Authors: Igor Zhirkov, Andrejs Petruhins, Anders Eriksson, Martin Dahlqvist, Arni Sigurdur Ingason, Johanna RosenAbstract:DC arc plasma from Ti, Al, and Ti1-xAlx (x = 0.16, 0.25, 0.50, and 0.70) compound Cathodes was characterized with respect to plasma chemistry and charge-state-resolved ion energy. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the deposited films and the Cathode surfaces were used for exploring the correlation between Cathode-, plasma-, and film composition. Experimental work was performed at a base pressure of 10−6 Torr, to exclude plasma-gas interaction. The plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the Cathode composition, while deposited films were in accordance with the Cathode stoichiometry. This may be explained by presence of neutrals in the plasma/vapour phase. The average ion charge states (Ti = 2.2, Al = 1.65) were consistent with reference data for elemental Cathodes, and approximately independent on the Cathode composition. On the contrary, the width of the ion energy distributions (IEDs) were drastically...
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characterization of plasma chemistry and ion energy in cathodic arc plasma from ti si Cathodes of different compositions
Journal of Applied Physics, 2013Co-Authors: Anders Eriksson, Igor Zhirkov, Martin Dahlqvist, Jens Jensen, Lars Hultman, Johanna RosenAbstract:Arc plasma from Ti-Si compound Cathodes with up to 25 at. % Si was characterized in a DC arc system with respect to chemistry and charge-state-resolved ion energy. The plasma ion composition showed a lower Si content, diverging up to 12 at. % compared to the Cathode composition, yet concurrently deposited films were in accordance with the Cathode stoichiometry. Significant contribution to film growth from neutrals is inferred besides ions, since the contribution from macroparticles, estimated by scanning electron microscopy, cannot alone account for the compositional difference between Cathode, plasma, and film. The average ion charge states for Ti and Si were higher than reference data for elemental Cathodes. This result is likely related to TiSix phases of higher cohesive energies in the compound Cathodes and higher effective electron temperature in plasma formation. The ion energy distributions extended up to ∼200 and ∼130 eV for Ti and Si, respectively, with corresponding average energies of ∼60 and ∼30 eV. These averages were, however, not dependent on Si content in the Cathode, except for 25 at. % Si where the average energies were increased up to 72 eV for Ti and 47 eV for Si.
Baikun Li - One of the best experts on this subject based on the ideXlab platform.
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cobalt porphyrin based material as methanol tolerant Cathode in single chamber microbial fuel cells scmfcs
Journal of Power Sources, 2014Co-Authors: Cristian Bruckner, Carlo Santoro, Yue Cheng, Baikun LiAbstract:This study focused on the development of novel Cathode material based on the pyrolysis of [meso-tetrakis(2-thienyl)porphyrinato]Co(II) (CoTTP) for use in single chamber microbial fuel cells (SCMFCs) to treat wastewater containing methanol. The Cathodes produced at two loadings (0.5 and 1.0 mg cm � 2 ) were examined in batch mode SCMFCs treating methanol of different concentrations (ranging from 0.005 to 0.04 M) over a 900 h operational period. Methanol was completely removed in SCMFCs, and the cycle duration was prolonged at high methanol concentrations, indicating methanol was used as fuel in SCMFCs. Methanol had more poisoning effects to the traditional platinum (Pt) Cathodes than to the CoTTP Cathodes. Specifically, power generations from SCMFCs with Pt Cathodes gradually decreased over time, while the ones with CoTTP Cathodes remained stable, even at the highest methanol concentration (0.04 M). Cathode linear sweep voltammetry (LSVs) indicated that the electrocatalytic activity of the Pt Cathode was suppressed by methanol. Higher CoTTP loadings had similar open circuit potential (OCP) but higher electrocatalytic activity than lower loadings. This study demonstrated that methanol can be codigested with wastewater and converted to power in MFCs, and a novel Cathode CoTTP catalyst exhibits higher tolerance towards methanol compared with traditional Pt catalyst. Published by Elsevier B.V.
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activated carbon nanofibers acnf as Cathode for single chamber microbial fuel cells scmfcs
Journal of Power Sources, 2013Co-Authors: Carlo Santoro, Astrid Stadlhofer, Viktor Hacker, G Squadrito, Uwe Schroder, Baikun LiAbstract:The suitability of carbon nanofibers (CNF) based Cathodes as alternative to the platinum (Pt)-based Cathode in single chamber microbial fuel cells (SCMFCs) were extensively studied over 3-month operational period. MFCs were fed with two solutions: synthetic wastewater (phosphate buffer (PBS) plus sodium acetate) and real wastewater (mixed liquor suspendedsolid (MLSS) solution). CNFs were chemically activated using HNO3 and then hot pressed on a carbon cloth support to increase surface area. The Cathode polarization showed a better behavior of the clean Pt-based Cathode in abiotic conditions. The activation of the nanofibers (ACNFs) gave an advantage to the Cathode performances compared to the raw CNFs. The SCMFCs fed with PBS showed four times higher power generation compared to MLSS solution. All the Cathodes showed a decrease in performances over time, and the advantage of the Pt over CNF/ACNF disappeared. CNF/ACNF Cathodes showed more stability in performances in long time operations. Biofilm formation, salt precipitations on the Cathode, and the presence of hydrogen sulfide decreased the activity of Pt Cathodes. A degradation and Pt detachment were noticed on Pt Cathodes over time. In contrast, CNF/ACNF Cathodes exhibited less deterioration throughout the operational period, which demonstrated a great potential as cost-effective Cathodes for long-term operation.
L. Bárdoš - One of the best experts on this subject based on the ideXlab platform.
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thin film processing by radio frequency hollow Cathodes
Surface & Coatings Technology, 1997Co-Authors: L. Bárdoš, Hana Barankova, Soren BergAbstract:Abstract The main features of the radio frequency (RF) hollow Cathodes for thin film processing are summarized. The utilization of cylindrical RF hollow Cathodes in both the plasma-enhanced chemical vapour deposition (PECVD) and the physical vapour deposition (PVD) of films is reviewed. An example of the high rate PECVD of Si–N films is described in more detail. Gas metastables excited inside the Cathode can act as a source of additional heat, thereby enhancing the thermionic electron emission and ionization of the gas. Transition from the glow into a hot Cathode arc regime is characterized by changes in the plasma parameters and consequently in the growth of films. Examples for PVD of TiN films are shown. Magnetic focusing in the linear arc discharge source leads to the formation of linear hot zones at the outlet of the parallel-plate Cathode and enables the hollow Cathode discharges to be scaled up for large area applications.
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Radio frequency hollow Cathodes for the plasma processing technology
Surface and Coatings Technology, 1996Co-Authors: L. BárdošAbstract:The present paper summarizes the main features of the hollow Cathode discharges generated by a radio frequency (r.f.) instead of a d.c. field. The pressure of gas inside the hollow Cathode is almost independent on the reactor pressure, which allows to generate discharge at high collision frequency and transport it into the low pressure reactor. The discharge forced out from the hollow Cathode forms a decaying plasma channel with extraordinary properties. Gas metastables excited inside the Cathode can act in selected gas mixtures as a source of additional heat, thereby enhancing thermionic electron emission and ionization of the gas. An arc regime can be started from the glow discharge simply by increasing the r.f. power. Hollow Cathode arc in the Cathode metal vapor can be sustained even without working gas. Examples of utilization of hollow Cathodes in the film deposition and dry etching technology are presented. Small size cylindrical r.f. Cathodes allow special applications inside narrow (< 10 mm in diameter) tubes. Linear arc discharge (LAD) produced by r.f. hollow Cathode with magnetic focusing promises new applications either with or even instead of magnetrons.
