Molecular dynamics simulations of surface modification formations on polycrystalline Cu under high electric fields

TL;DR

This study uses molecular dynamics simulations to investigate how surface protrusions form on polycrystalline copper under high electric fields, revealing the influence of grain boundaries and temperature on protrusion growth.

Contribution

It demonstrates the role of grain boundaries and temperature in protrusion formation on copper surfaces under electric stress, providing new insights into vacuum breakdown mechanisms.

Findings

Protrusions can grow under electrostatic stress on copper surfaces.

Grain boundaries significantly influence protrusion formation.

Protrusion formation time increases with decreasing electrostatic field.

Abstract

Vacuum breakdowns in particle accelerators and other devices operating at high electric fields is a common problem in the operation of these devices. It has been proposed that the onset of vacuum breakdowns is associated with appearance of surface protrusions while the device is in operation under high electric field. Moreover, the breakdown tolerance of an electrode material was correlated with the type of lattice structure of the material. In the current paper we conduct molecular dynamics simulations of nanocrystalline copper surfaces and show the possibility of protrusion growth under the stress exerted on the surface by an applied electrostatic field. We show the importance of grain boundaries on the protrusion formation and establish a linear relationship between the necessary electrostatic stress for protrusion formation and the temperature of the system. We show that time for protrusion formation increases with the lowering electrostatic field and give the Arrhenius extrapolation to the case of lower fields. General discussion of the protrusion formation mechanisms in the case of polycrystalline copper surfaces is presented.