A microscopic study into the role of grain boundaries in field-assisted protrusion growth and potential for current fluctuations in electron nanoemitters

Studies of metallic field emission devices during operation have reported fluctuations in current and local luminosity across the emitting surface that suggest a time-dependent evolution of surface structure and morphology. One possibility is the growth of surface nanoprotrusions (NPs) driven by high Maxwell stress arising from the externally applied electric field. This aspect is probed through three-dimensional, time-dependent molecular dynamics simulations for a quantitative predictive analysis. Our results indicate NP growth for electric fields at levels of 5 × 108 V/m or higher. Material ejection from NPs is also shown to be likely for high fields acting over an extended duration. The trends agree qualitatively with reports in the literature, demonstrating the role of grain boundaries as an enabling mechanism, showing that NP growth is synergistically strengthened by the presence of surface voids, and the possibility of dynamic current fluctuations.