Linear arrays of ceramic microcavity plasma devices (127-180 μm diameter) driven by buried coplanar electrodes: Shaping the intracavity electric field and emission profile

Shaping the electric field within a microcavity plasma device can be accomplished by the introduction of curvature into the dielectric-plasma interface when the microcavity is inserted between coplanar electrodes. To that end, linear arrays of cylindrical microcavity plasma devices with diameters of 127 or 180 μm have been fabricated in low temperature cofired ceramic (ε _r=40) and operated in the rare gases at pressures in the 400-800 Torr range. Comprising 72 microcavities, each linear array is powered by two buried Ag electrodes lying parallel to the array and driven by either a sinusoidal ac or bipolar pulsed dc waveform. Examination of Ne microplasmas with an optical telescope reveals the existence of pressure-dependent structure on the spatially resolved emission profiles. Strongest emission is observed from two negative glows on opposite sides of the microcavity. Confined to regions of low electric field strength and a weak gradient, the negative glows generate maximum intensity 25-35 μm from the wall of a 180 μm diameter microcavity. A central peak appears along the longitudinal axis of symmetry of the microcavity for p _Ne ≳ 700 Torr, reflecting the formation of a positive column. Operating voltages as low as 190 V rms have been measured for excitation of a linear array of 180 μm diameter devices operating at a Ne pressure of 400-700 Torr and driven by a 20 kHz voltage waveform.