Current Density Enhancements from Silicon Based Micro-Hollow Cathode Discharges for Application as an Electron Source

A silicon micro-electro-mechanical systems (MEMS) process was developed to fabricate micro-hollow cathode discharges (MHCD). The process resulted in baseline devices in which bulk silicon served as the hollow cathode material. Two cathode coating processes were developed to coat the silicon with more ideal cathode materials. These processes applied a thin film coating of either aluminum oxide or titanium silicide to the silicon cathode surface. Fabricated devices were tested to investigate the effect of cathode material and operating conditions on MHCD performance and lifetime. High performing, long lasting MHCDs were investigated for use as an electron source amongst other possible applications.;Data collected in this study suggested that electron tunneling enabled direct current glow discharge operation from dielectrically-coated cathodes. This was observed when the thin film dielectric was thin enough that conditions were favorable for tunneling. This research demonstrated that cathodes coated with aluminum oxide yielded increases in current density of up to 60% over silicon and titanium silicide-coated cathodes operating at similar conditions. The increase in current density was attributed to the high secondary electron yield of the dielectric aluminum oxide coating.;In addition to increasing current density, the cathode coatings developed here led to an increase in cathode lifetime and robustness. The cathode coatings helped mitigate the failure mechanism of silicon-based micro-hollow cathode discharges. The low sputter yield of both aluminum oxide and titanium silicide was shown to at least double the lifetime and maximum operating pressure of coated micro-hollow cathodes. Coated cathodes could be operated up to pressures of 150 Torr, three times the operating pressure that baseline silicon cathodes survived to.;Additionally, a linear relationship between MHCD operating pressure and cathode current density was observed. The data were collected from a single cathode cavity at a constant current of 0.6 mA and at operating pressures ranging from 30 Torr to 150 Torr. When extrapolated out to atmospheric pressure, the relationship predicted MHCD current densities near 1 A/cm 2.