Cold-Cathode Electron Field Emission of Boron Nitride Thin Film with a MEMS-based Gate for Space Applications

Abstract

Cold-cathode electron field emission is a technology emerging as an appealing alternative to high power thermionic emitters and gas plasma contactors that use a consumable (Xe gas, typically) for space electrodynamic tether systems and other space electric propulsion systems requiring low-power neutralizers. Example cold-cathode electron field emission technologies include Spindt-type cathodes and gated carbon nanotubes, both of which emit electrons through quantum mechanical tunneling of electrons, instigated by a high electric field applied at the emitter surface. Research at the University of Michigan indicates that nanostructured Boron Nitride (BN) is an attractive material for cold-cathode electron emission due to its low work function, structural robustness, chemical inertness (Spindt -type cathodes with Mo tips are known to degrade in an oxygen environment), and favorable emission characteristics. To facilitate the acceleration of electrons away from the emission surface and toward the plasma anode (beyond the space charge limit), a MEMS -based gated structure has been developed in order to provide the high surface electric fields required for electron emission at the BN surface. This paper will describe the integrated device development for a gated BN emitter to be used in the student-designed Field Emission Get-Away-Special Investigation (FEGI) project- a test platform for low-earth demonstration of various coldcathode electron field emitter designs.