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 20 m. 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 with HGPD thin-films, and these new, on-chip devices operate at similar current magnitudes of 100 nA to 5 A. 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. 1 Corresponding author and currently Assistant Professor, Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA email: [email protected] Planar microscale ionization devices in atmospheric air with diamond-based electrodes 2