Post-ion beam induced degradation of copper layers in transmission electron microscopy specimens

Copper containing transmission electron microscopy (TEM) specimens frequently show corrosion after focused ion beam (FIB) preparation. This paper reveals that the corrosion product is a Cu–S phase growing over the specimen surface. The layer is identified by energy-dispersive x-ray spectroscopy, and lattice spacing indexing of power spectra patterns. The corrosion process is further studied by TEM on cone-shaped specimens, which are intentionally stored after FIB preparation with S flakes for short time. Furthermore, a protective method against corrosion is developed by varying the time in the FIB vacuum and the duration of a subsequent plasma cleaning.