科研之友
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摘要
In recent studies, it has been shown that cold field emission can be an important electron source in microscale discharges. However, if the cathode is heated to a high temperature, thermal emission also becomes significant, which impacts microscale discharge formation. Importantly, in both cold and thermal conditions, the local electric field at the cathode impacts the emission current, and ionization in the discharge can create sufficient space charge to modify the electric field. In this work, a simple two-fluid model is used to evaluate the impact of thermal emission on discharge properties at microscale dimensions. We incorporate two thermal emission models-the 'low field' Schottky emission model, which assumes electron tunneling is negligible, and the 'high field' thermo-field emission model, which accounts for tunneling-in order to accurately predict thermal emission in the microdischarge. We evaluate the impact of ionization on the thermal emission in a microdischarge and find that the presence of positive ions increases emission current, and this effect becomes more pronounced as either the applied voltage or the cathode temperature is increased. The enhanced emission causes breakdown to occur at significantly lower voltages than predicted by the classic Paschen's curve or the more recent modified Paschen's curve that accounts for cold field emission, highlighting how thermal emission can induce substantially different discharge behavior.
- 出版日期2016-2-10
