Plasma parameters of MSE sustained high pressure glow discharges

Summary form only given, as follows. In order to generate large area, DC driven glow discharges at elevated pressures, micro-structure-electrode (MSE) arrays have been implemented. The currently used microstructures consist of a matrix of holes perforated in a thin multilayer system made out of two metallic foils (copper) separated by a dielectric spacer (Kapton). Typical dimensions are: holes diameter 100 /spl mu/m, electrodes thickness 100 /spl mu/m, 50 /spl mu/m thick insulator and holes pitch 0.75 to 3 mm. Direct current microdischarges were produced in noble gases (e.g. argon, helium neon), air and mixtures thereof at pressure ranging from hundreds of mbar up to one atmosphere. The discharge current can vary from 0.1 to 20 mA/per hole at operation voltage around 200 V, leading to a current density up to 100 A/cm/sup 2/. Single discharges and arrays of up to 200 microdischarges without individual resistive ballast have been successfully operated. Current-voltage characteristics and the optical appearance are proving a stable, non-filamentary glow discharge but they are not giving any information about the plasma parameters. In order to estimate the electron density, electron temperature and gas temperature a single Ar discharge has been investigated via optical emission and absorption spectroscopy. The emission spectrum consists mainly of atomic transitions but spectral lines from singly charged ions are also present, revealing the presence of energetic electrons. The electron density was obtained from the analysis of Stark-broadened profiles of hydrogen Balmer spectral lines. Absorption measurements have been performed using a tunable diode laser as a light source. The absorption line profiles of neutral argon spectral lines (3p/sup 5/4p-3p/sup 5/4s transitions) have been studied. The MSE arrays are providing a non-equilibrium high pressure plasma which is very promising for surface processing and gas phase plasma chemistry.