Micro-structured electrode arrays: atmospheric pressure plasma processes and applications

Micro-structured electrode (MSE) arrays allow to generate large-area uniform glow discharges over a wide pressure range up to atmospheric pressure. The electrode dimensions in the micro-range realized by means of modern micro-machining and galvanic techniques are small enough to generate sufficiently high electric field strengths to ignite gas discharges applying only moderate radio frequency (13.56 MHz) voltages (80–390 V in Ne, He, Ar and N2). The non-thermal plasma system is characterized by a special probe measuring the electric parameters. Possible industrial applications of the MSE arrays are plasma chemistry (e.g. waste gas decomposition) and surface modification of materials. Using an MSE based micro-reactor the abatement of the greenhouse gas CF4 was performed with decomposition rates of over 90% at a pressure of 100 mbar in He and N2. The decomposition of waste gases in the plasma was monitored online with quadrupole mass spectrometry. At atmospheric pressure in He the abatement rate of CF4 is still over 70%. Other applications realized in our lab are thin film deposition of diamond-like carbon layers and SiO2 layers on various substrates and sterilization of food packaging materials.