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ABSTRACT: This article explores electric current and field distributions in dc microplasmas, which have distinctive characteristics that are not evident at larger dimensions. These microplasmas, which are powered by coplanar thin-film metal electrodes with 400-μm minimum separations on a glass substrate, are potentially useful for microsystems in both sensing and microfabrication contexts. Experiments in N2N2 ambient show that electron current favors electrode separations of 4 mm at 1.2 Torr, reducing to 0.4 mm at 10 Torr. The glow region is confined directly above the cathode, and within 200–500 μm of its lateral edge. Voltage gradients of 100 kV/m exist in this glow region at 1.2 Torr, increasing to 500 kV/m at 6 Torr, far in excess of those observed in larger plasmas. Numerical simulations indicate that the microplasmas are highly nonquasineutral, with a large ion density proximate to the cathode, responsible for a dense space-charge region, and the strong electric fields in the glow region. It is responsible for the bulk of the ionization and has a bimodal electron energy distribution function, with a local peak at 420 eV. © 2003 American Institute of Physics. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/69877/2/JAPIAU-94-5-2845-1.pdf
