A low-voltage high-pressure field ionizer for portable analytical instruments

Field ionization of helium is demonstrated at voltages as low as 150 V using large arrays of self-aligned gated tips. The operating voltages reported here are more than 3× lower than the best results reported in literature. These substantially reduced operating biases permit stable operation of the device at pressures as high as 1 Torr by avoiding arcing or plasma formation that can permanently damage the device. The fabricated arrays are composed of 320,000 nano-scale tips with radii below 5 nm. Ion current in nano-ampere-range, sufficient for most analytical instruments, can be produced with tip-to-gate biases below 200V. Long term (> 10⁴ s) ionization of helium was accomplished at 1 Torr pressures.