Controlling surface discharge patterns and plasma chemistry with a hexagonal electrode structure and gas composiiton

Summary form only given. Uniform discharge covering a large surface area is desirable for applications in materials processing and medicine. Surface discharge plasmas (SDP) is generated with a stainless steel electrode patterned with many identical hexagonal elements each having a diameter of 7mm, and is investigated from the stand point of discharge pattern and chemistry. Several gas mixtures are used made from He, Ar, N₂ and O₂ at atmospheric pressures and the sinusoidal plasma excitation is at 20 - 30 kHz. Electrical measurement, optical emission spectroscopy and high-speed imaging are employed to investigate the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Intriguing discharge patterns are observed under different discharge compositions. Unique discharge patterns are observed, through altering electrical power density and gas composition. The influence on the transitions of the discharge patterns is reported and discussed of the thickness of the dielectric layer, plasma-forming gas and input electrical power density