Microwave Breakdown of Nitrogen Gas in a Microgap
Dr. Stephen Remillard, Hope College
Dielectric breakdown of nitrogen gas in a microgap (specifically between 10 and 1000 microns) was found to be governed by different mechanisms than breakdown in large gaps. It is useful to characterize these mechanisms to identify regions of failure for MEMS (micro-electro-mechanical systems) devices. Pressure dependence of the breakdown electric field revealed a collisional pressure regime, which contains particles having frequent low-energy collisions resulting from the short mean free path of a high pressure gas, and collisionless pressure regime, which contains particles having infrequent high-energy collisions resulting from the long mean free path of a low pressure gas. As gap size was reduced, the collision frequency coefficient was found to depend exponentially on the pressure exponent. At large gaps (greater than 2540 microns) and at small gaps (less than 75 microns), the collision frequency coefficient and the pressure exponent level off, as gap size is varied, showing us that there are different limiting factors to the diffusion length of the plasma. Optical emissions reveal that different molecular excitations dominate the plasma at small and large gaps.
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