High current density MEMS deuterium ionizers

In this work, we report a high current density MEMS ionizer for deuterium that is based on an array of high aspect ratio field emitter microstructures. The Si field emitter structure has a unique device architecture that uses a high-aspect-ratio (∼50:1) silicon nanowire current limiter to regulate electron flow to each field emitter tip in the array. The nanowire diameter is 100–200 nm while the height is 10 μm. The gate electrode of the field emitter is supported by a 10 μm tall dielectric matrix while a 3–4 μm thick dielectric is under the contact pad and together they enable a bias of >300 V between the ionization tip and the gate without breakdown. Field emission characterization of field emitter arrays similar to this device show that the field factor, β, is > 1.2×10 6 cm −1 , which is consistent with electrostatic simulations using COMSOL. Analytical and numerical modeling of the structure based on the measured tip radius statistics, suggest that it is possible demonstrate a D+ ion source with high current (500 μA) at high current density of 12 mA/cm 2 in a compact volume while consuming less than 1 W.