UC Davis

In this work we investigate the suitability of insulating coatings as electron tunneling barriers onDC micro hollow cathode surfaces. Our hypothesis is that with a sufficiently thin insulating coating of sufficiently high dielectric strength, one might sustain the continuous current of a traditional DC glow discharge through an insulator’s relatively high secondary electron emission yield at the surface, while preventing surface charging through tunneling processes. We initially focus on aluminum oxide as a well-understood material with mature atomic layer deposition (ALD) and other semiconductor fabrication technologies. Several basic geometries are investigated, including planar disc cathodes and tubular hollow cathodes. Electrical results are compared with simple analytical models assuming a tunneling mechanism to allow DC current to pass through the insulating surface due to the applied electric field imposed by the plasma sheath. Furthermore, we verify that conduction and sustenance of cathode discharge not only occurs through tunneling, but also which thicknesses of insulating film are optimal. Micro-hollow cathode discharge devices were successfully fabricated and scaling relationships between number of pores were established. Later chapters cover the novel material 12CaO∙7Al2O3 (C12A7) which exhibits excellent room temperature emission and stability. Furthermore, early success towards the fabrication of C12A7 by ALD has been completed in hopes of incorporation into micro hollow cathode discharge (MHCD) devices in further work.