A corrosion study of nanocrystalline copper thin films

Thin nanocrystalline, compact films, based on the copper–nitrogen system, up to 2.5 μm thickness and 3.5% nitrogen, were deposited by magnetron sputtering at different partial pressure ratios of N2 and Ar, without formation of CuxN compounds, the nitrogen concentration influencing grain size (down to 30 nm) and film homogeneity. Electrochemical corrosion properties were investigated using polarization curves and electrochemical impedance spectroscopy in 0.5 M NaCl aqueous solution, and compared with pure bulk copper; morphology was examined by scanning electron microscopy. Significant variations in corrosion currents between samples were attributed to grain size and structural defects on the grain boundaries.

Research highlights
► Copper thin films formed by sputtering in presence of N2 alters nanocrystallinity.
► Corrosion behaviour of thin nanocrystalline films investigated.
► Greater corrosion rate for smaller copper grain size.
► Results important for application in electronic devices.