Abstract
The decrease in electronic device size necessitates greater understanding of gas breakdown and electron emission at microscale to optimize performance. While traditional breakdown theory using Paschen’s law (PL), driven by Townsend avalanche, fails for gap distance d lesssim 15 μm, recent studies have derived analytic equations for breakdown voltage when field emission and Townsend avalanche drive breakdown. This study derives a new analytic equation that predicts breakdown voltage VB within 4% of the exact numerical results of a previously derived theory and new experimental results at subatmospheric pressure for gap distances from 1–25 μm. At atmospheric pressure, VB transitions to PL near the product of pressure and gap distance, pd, corresponding to the Paschen minimum; at lower pressures, the transition to PL occurs to the left of the minimum. We further show that the work function plays a major role in determining which side of the Paschen minimum VB transitions to PL as pressure approaches atmospheric pressure while field enhancement and the secondary emission coefficient play smaller roles. These results indicate that appropriate combinations of these parameters cause VB to transition to PL to the left of the Paschen minimum, which would yield an extended plateau similar to some microscale gas breakdown experimental observations.
Highlights
Gas breakdown in the presence of electric fields is desirable for generating microplasmas for combustion[1], electric propulsion[2], or medical and environmental applications[3,4,5,6,7] and deleterious in accelerators[8], fusion devices[9], micro and nanoelectronics[10,11], and pulsed power biological experiments[12]
We generated the nanosecond pulse by feeding DC voltage into a high voltage solid-state switch (BEHLKE HTS-50-08-UF), which delivered adjustable nanosecond pulses with a maximum amplitude up to 5 kV
Using β as a fitting parameter, we achieved excellent agreement between the exact numerical solution of the theory and the experimental results, and demonstrated that the analytic model differed from experiment by an average of 3.71%
Summary
The experimental system consists of a nanosecond pulse generation unit, a synchronous and delay triggering unit, an in-situ optical imaging unit, and an electrical parameter measurement unit. We integrated an in-situ optical imaging unit with an optical microscope to achieve micron-scale spatial resolution and a high-speed gated ICCD camera to attain nanosecond-scale temporal resolution. We used a high-speed gated ICCD camera (ANDOR iStar 334 T) to detect light emission during gas breakdown with a minimum gate width of 2 ns. This letter focuses on breakdown measurements; further experimental assessments will be reported elsewhere. When plotted as a function of d, VB is relatively insensitive to p at smaller gap distances where one anticipates field emission driven breakdown. AFN and BFN are Fowler-Nordheim constants, Ap and Bp are gas constants, m is the mass of the gas atom in kg, σCE isthe charge exchange cross section, e
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