Edge effect on the current-temperature characteristic of thermionic cathodes

TL;DR

This study uses molecular dynamics simulations to analyze how the finite size of thermionic cathodes influences the current-temperature characteristic, revealing edge effects that smooth the transition in Miram curves.

Contribution

It introduces a computational model showing how edge effects and emitter size impact the shape of Miram curves in thermionic cathodes.

Findings

Edge effects cause smoothing of the Miram curve transition.

Smaller emitters produce softer knees in the Miram curve.

Edge emission significantly influences current-temperature characteristics.

Abstract

We perform a computational study, based on the molecular dynamics method, of the shape of Miram curves obtained from microscale planar diodes. We discuss the smooth transition from the source-limited to space-charge-limited regime due to the finite size of the emitter, i.e. the "knee" in the Miram curve. In our model we find that the smoothing occurs mostly due to the increased emission at the external edges of the emitting area, and that the knee becomes softer when the size of the emitting area decreases. We relate this to the recent work which has described how a heterogeneous work function similarly affects the Miram curve.