Planar Microscale Ionization Devices in Atmospheric Air with Diamond-based Electrodes

Planar microscale ionization devices that operate in atmospheric air have been developed out of highly graphitic polycrystalline diamond (HGPD). The devices have been fabricated on both silicon and quartz substrates with electrode gaps ranging from 5 to 20μm. Experiments show that the HGPD devices operate in the pre-breakdown regime where a field-emission mode enables appreciable ionization current without the occurrence of sparks or breakdown. The devices are compared to prior experiments that used HGPD thin films and these new, on-chip devices operate at similar current magnitudes of 100 nA–5μA. For comparison, titanium planar ionization devices have also been fabricated and tested. However, these devices were unable to operate at any appreciable current without the formation of spark discharges. These results suggest that HGPD is a good candidate material for integrated, on-chip ionization devices for applications including miniature mass spectrometry, gas sensing and microscale electrohydrodynamics