Micro-Structured Electrode Arrays: Characterization of High Frequency Discharges at Atmospheric Pressure

Summary: Micro-structured electrode (MSE) arrays allow large area uniform glow discharges to be generated over a wide pressure range up to atmospheric pressure. Electrode widths, thicknesses and distances in the μm-range are realized by means of modern micro machining and galvanic techniques. These electrode dimensions are small enough to generate sufficiently high electric field strengths to ignite gas discharges by applying only moderate radio frequency (RF, 13.56 MHz) voltages (80 V to 390 V in Ne, He, Ar, N2 and air). The non-thermal plasma system can be characterized by a special probe measuring the electric parameters. MSE driven plasmas demonstrate different behavior from conventional RF or DC discharge plasmas. Due to the very small electrode gap width, d, the behavior of the charged particles in the RF field of our system could be described with the DC Townsend breakdown theory. Partially, dependent on the pressure range and type of gas, the breakdown mechanism was dominated by field electron emission or by a high frequency regime. The voltage-current characteristic and electron density of the MSE plasma in He at atmospheric pressure were characteristic for a glow discharge. Using MSE arrays as plasma sources, several applications have been developed and successfully tested including atmospheric pressure plasma chemistry (decomposition of waste gases like CF4 and NO) and the sterilization of food packaging materials at atmospheric pressure. Voltage-current characteristic of a 100 kPa He RF glow discharge generated with an MSE array (d = 70 μm).