Dovetail Tip: A New Approach for Low-Threshold Vacuum Nanoelectronics

An innovative approach for the fabrication of low-threshold, nanoscale field-emitter cathodes and arrays is proposed. By shaping a titanium cathode as dovetail geometry and using a thin vertical wall of high-permittivity dielectric, Si₃N₄, to isolate the tip from the gate, the electric field intensity near the tip edges is strongly increased, and a turn-ON voltage in the range of a few volts is predicted numerically and observed experimentally. The resulting cathode structure is compact, self-aligned to the vacuum cavity and is fabricated through the standard silicon fabrication processes. Besides, unlike all existing approaches, vacuum is achieved at the wafer level and not at the package level, thereby reducing fabrication costs. Measurements on a first prototyped array of 5×4 diode-connected parallel devices with a silicon area of 5 μm×4 μm, confirm Fowler-Nordheim emission with a 2 V turn-ON voltage, while displaying a total emission current of 25 μA at a gate-cathode bias of 20 V.