Abstract:

While Paschen’s law is commonly used to predict breakdown voltage, it fails at microscale gaps when field emission becomes important. Accurate breakdown voltage predictions in the microscale regime are even more important with the trend of decreasing electronic device dimensions. Developing analytic models to accurately predict breakdown at microscale is vital for understanding the underlying physics occurring within the system and to ensure the prevention or production of a discharge, depending on the application. We first take a pre-existing breakdown model coupling field emission and Townsend breakdown and present a matched asymptotic analysis resulting in analytic equations for breakdown voltage in argon at atmospheric pressure. Next, we extend the model for argon at atmospheric pressure to generalize for gas and further explore the independent contributions of field emission and Townsend discharge. Finally, we present analytic expressions for breakdown voltage valid for any gas at any pressure, and discuss the modified Paschen minimum occurring at microscale. The presented models show excellent agreement with numerical and simulation results, and agree well with experimental data when using the field enhancement factor as a fitting parameter. The work presented in this thesis is a first step in unifying gas breakdown across length scales and breakdown mechanisms. Future work will aim to incorporate other breakdown mechanisms, such as quantum effects or space-charge limited flow, to provide a more complete unified model for gas breakdown.

Bio:

Amanda Loveless has been honored with the 2017 IEEE Nuclear & Plasma Sciences Society (NPSS) Graduate Scholarship Award. Loveless is a graduate student in the School of Nuclear Engineering at Purdue University, where she is advised by Dr. Allen Garner, Assistant Professor of Nuclear Engineering. Loveless received this award for theoretical modeling of electrical breakdown in gases in microscale gaps.  She performed a matched asymptotic analysis of a model unifying field emission with Townsend avalanche that matched simulation and experimental results across a wide range of gap distances and pressures while quantitatively and analytically demonstrating the transition from field emission to the classical Paschen law.  Her work demonstrates the fundamental physics in small scale devices that will aid researchers interested in either generating microplasmas or avoiding breakdown in micro- and nanoelectronics. Loveless’s research is supported by a Junior Faculty Development Grant from the Nuclear Regulatory Commission.  She has also received the 2016-2017 Otto F. and Jenny H. Krauss Scholarship and the 2016-2017 IEEE Dielectric and Electrical Insulation Society Fellowship for her proposal on modeling RF breakdown