Planar microscale ionization devices in atmospheric air with diamond-based electrodes

Abstract

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.

Direct simulation of ionization and ion transport for planar microscale ion generation devices

“…The electrodes are modeled as 1 µm thick and 50 µm wide with a gap spacing of 10 µm [16]. The electrodes are placed on a dielectric layer.…”

“…The parameters β, the local field enhancement factor due to microscale features on the cathode surface, and , the work function of the surface, are properties of the cathode material. Because experiments suggest HGPD as a favorable material for planar microscale ion generation devices [16], a work function of  = 4.60 eV is used based on the work function of graphite, which has previously been used to represent the effective work function of highly graphitic polycrystalline diamond films [47]. In this work,  is chosen so that a specific emission current is obtained, and therefore the impact of the emission current can be accurately studied.…”

Experimental Study on Electrical Breakdown for Devices with Micrometer Gaps

“…The discharge would result in unexpected currents (especially for those devices driven by electrostatic force), degrade the performance or completely destroy the devices. Recent studies have focused on the breakdown phenomenon which occurs at micron-scale dimensions, where two electrodes exposed to air are spaced less than 20 µm apart [4] . Therefore, a thorough understanding of how breakdown occurs in the micrometer gaps is very important in reducing the risk of device failure.…”

Multiphysics simulation of corona discharge induced ionic wind

“…For example, Adamiak and others [2,3,4,5] studied the DC and pulsed corona discharge between a needle and a plate collector, using different numerical methods (FEM, BEM, FCT etc.) for the approximation of each equation in the PDE system; Ahmedou and Havet [6,7,8] used a commercial FEM software to investigate the effect of EHD on turbulent flows; Moreau and Touchard, [9] Huang and others, [10] and Kim and others [11] experimentally studied different EHD devices designed for cooling or air pumping purpose; Chang, Tsubone and others [12,13,14] made extensive experimental study of the forced airflow and the corona discharge in a converging duct; Jewell-Larsen and others [15,16,17,18,19,20,21] and Go and others [22,23,24,25,26] conducted both experimental and numerical studies aimed at designing and applying ionic wind cooling devices to thermal management of electronic devices.…”