Study of Nanoscale Microprotrusions on Metal Electrode Surfaces Under High Electric Fields

Microprotrusions under high electric fields are considered to be sources of metal vapor and microplasma on metal electrode surfaces and may even initiate vacuum breakdown in vacuum gaps. The mechanism of the phenomena has been studied for a long time. However, the dynamic evolution processes of microprotrusions under high electric fields considering the influence of the material properties are still not clear. The objective of this article is to study the dynamic evolution processes of the nanoscale microprotrusions on Cu and Cr electrode surfaces under high electric fields based on atomistic modeling. With considering the electron emission heating, surface charge, Coulomb, and electric field forces, a 3-D numerical model is established by coupling molecular dynamics (MD) and finite difference method (FDM), for simulating the dynamic evolution processes of the microprotrusions under high electric field. Furthermore, the influence of material properties on the dynamic evolution processes is discussed and compared between Cu and Cr. The simulation results show that the heating effect of the electron emission induced by an intense electric field could lead the microprotrusions to localized melting and subsequent elongation and may finally generate metal vapor in the vacuum gap. In addition, the material properties have a significant influence on the field-induced dynamic evolution processes of microprotrusions.