Nanofabricated Low-Voltage Gated Si Field-Ionization Arrays

We demonstrate high-density (1-
$\mu \text{m}$
pitch) silicon field-ionization arrays (FIAs) with self-aligned gate apertures (350 nm in diameter) and integrated nanowire current regulators. Our FIAs achieved high field factors (>0.1 nm
⁻¹
) and significantly lower ionization voltages (<100 V) than the devices with lower tip densities previously reported. Ion currents were measured in argon, deuterium, and helium at pressures from 1 to 16 mTorr. The FIAs turned on between 70 and 85 V, and the ion currents of around 0.4 nA were measured at 100 V. Higher currents of 7 nA were obtained at 147 V and 16 mTorr, but with the risk of gate damage by the ions energized in the intense gate-ionizer field. Si FIAs coated with Pt resulted in higher field factors due to sharper tips, but lower ion currents. Surface states, coupled with molecular adsorption and transport to the ionizer, are the possible mechanisms for lower voltage ionization in the uncoated Si FIAs.