Prebreakdown and breakdown characteristics of micrometric vacuum gaps between broad area electrodes

The DC prebreakdown and breakdown characteristics of micrometric gaps varying from 25 to 1000 μm, between highly polished 2 cm-diameter sphere electrodes, were extensively investigated at ~10^-5 Torr. The I-V characteristics of the above gaps obey Fowler-Nordheim behaviour confirming that the prebreakdown conduction was dominated by high field electron emission. The breakdown voltage derived from the prebreakdown data took the form of the power relation of gap distance as V_h=Kd^α. The breakdown strength of a 50 μm gap was as high as 220 V/μm, which is the highest value reported in literature for broad area electrodes. The breakdown strength decreases as the gap distance increases, with a 1000 μm gap breaking down at 44.5 V/μm. Results of this work are valuable for the design of vacuum gaps in Field Emission Displays