Different Types of Atmospheric Pressure Plasmas for Material Processing

The following are articles, papers and publications discussing different types of atmospheric pressure plasmas for material processing and surface treatment compared to vacuum plasma. The types of atmospheric plasma technology discussed included radio frequency (RF) capacitive discharge plasma, non-thermal plasma, thermal plasmas, DC plasmas, transferred arcs, plasma torches, corona discharges, and dielectric barrier discharges.

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Selwyn, G. S., Herrmann, H. W., Park, J., and Henins, I., “Materials processing using an atmospheric pressure, RF-generated plasma source,” Contrib. Plasma Phys. 6, 610 (2001). Abstract: Processing materials at atmospheric pressure provides clear advantages over traditional, vacuum-based plasma processing: in addition to reduction in the capital cost of equipment and the elimination of constraints imposed by vacuum-compatibility, high pressure and low temperature plasma processes offer unprecedented improvements for generation of active chemical species, high chemical selectivity, minimal ion densities resulting in low surface damage and surface treatment methods unattainable by other means. We describe several variations of this unique plasma source and some of its potential applications.
Laroussi, M., and Akan, T., “Arc-free atmospheric pressure cold plasma jets: a review,” Plasma Process.Polym. 4, 777 (2007). Abstract: Non-thermal atmospheric pressure plasma jets/plumes are playing an increasingly important role in various plasma processing applications. This is because of their practical capability to provide plasmas that are not spatially bound or confined by electrodes. This capability is very desirable in many situations such as in biomedical applications. Various types of ‘cold’ plasma jets have, therefore, been developed to better suit specific uses. In this paper a review of the different cold plasma jets developed to date is presented. The jets are classified according to their power sources, which cover a wide frequency spectrum from DC to microwaves. Each jet is characterized by providing its operational parameters such as its electrodes system, plasma temperature, jet/plume geometrical size (length, radius), power consumption, and gas mixtures used. Applications of each jet are also briefly covered.
Laimer, J., and Störi, H., “Recent advances in the research on non-equilibrium atmospheric pressure plasma jets,” Plasma Process.Polym. 4, 266 (2007). Abstract: Recently, there has been increased interest in using atmospheric pressure plasmas for materials processing, since these plasmas do not require expensive vacuum systems. However, APGDs face instabilities. Therefore, special plasma sources have been developed to overcome this obstacle, which make use of DC, pulsed DC and AC ranging from mains frequency to RF. Recently, the APPJ was introduced, which features an α-mode of an RF discharge between two bare metallic electrodes. Basically, three different geometric configurations have been developed. A characterization of the APPJs and their applications is presented.
S. Y. Moon, J. W. Han, W. Choe., “Feasibility study of material surface treatment using an atmospheric large-area glow plasma.” Thin Solid Films 506– 507 (2006) 355 – 359. Abstract: Application of atmospheric large-area plasma of a volume of 200 × 50 × 4 mm3 to various material surfaces was attempted for modification of surface properties. Based on the electrical and optical diagnostics, the plasma used for the treatment exhibited normal glow discharge characteristics with relatively low gas temperature, which might enable surface modification without thermal effect. Contact angle measurement showed that the plasma treatment, in general, changed surface characteristics such as wettability of paper, glass, and a silicon (Si) wafer from being hydrophobic to hydrophilic. In addition, ashing of the photoresist coated on a Si demonstrated that the measured ashing rate was found to vary depending on the plasma exposure time and the oxygen amount added to the argon supply gas. Based on the results, it is expected that the atmospheric plasma can be effectively utilized to some processes to which conventional low-pressure plasmas are employed.
Kogelschatz, U., “Applications of microplasmas and microreactor technology,” Contrib. Plasma Phys.47, 80 (2007). Abstract: During the last decade a number of microcavity plasma devices have been developed. Examples are microhollow cathode (MHC) discharges and cathode boundary layer (CBL) discharges proposed by Schoenbach, capillary plasma electrode (CPE) discharges proposed by Kunhardt and Becker, and micro-structured electrode arrays (MSEs) introduced by Gericke and Penache. Arrays of microplasmas based on silicon, ceramic, or metal/polymer structures were investigated by Eden, Frame, Park and coworkers. A breakthrough in the life expectancy of such devices was achieved when all metal electrodes were covered by dielectrics, thus combining dielectric-barrier discharge technology with microcavity plasma devices. The advantage of this technology is that large numbers of miniature atmospheric-pressure non-equilibrium discharges can be operated in parallel. Applications include emitters for visible and UV radiation, photodetectors, sensors, decontamination, surface modification, etching, film deposition, generation of nanoparticles. Operated in different gas mixtures many of these devices proved to be efficient emitters of ultraviolet excimer radiation. If a small gas flow is fed through these microplasmas applications for plasmachemical synthesis and pollution control become feasible. Novel applications are expected from the combination of microreactor technology with non-equilibrium plasma chemistry. Doping or coating of the dielectric surfaces results in additional catalytic effects.