Reduction of copper surface oxide using a sub-atmospheric dielectric barrier discharge plasma

Abstract

Oxide layers on metal surfaces adversely affect processability and material properties in many industrial applications. Although several plasma-based approaches for deoxidation were investigated in the past, oftentimes they either work under conditions expensive to create or require long processing times. In this study, the deoxidation effect of a non-thermal dielectric barrier discharge plasma in an Ar/H2 gas mixture at 100 hPa and 20 °C was investigated on copper surfaces with a native oxide layer. The chemical structure of surfaces before and after deoxidation was analyzed by X-ray photoelectron spectroscopy (XPS). The results revealed that ∼98% of the surface lattice oxide Cu2O was reduced to Cu after around 20 s of plasma treatment, whereas all oxygen contaminants were almost completely removed from Cu surface after around 50 s. Additionally, the kinetics of the reduction of surface oxide was studied and a Johnson-Mehl-Avrami-Erofeev-Kholmogorov kinetic model was proposed. The analysis of the morphology of surfaces was performed with atomic force microscopy (AFM), showing minor changes in the roughness after deoxidation. Moreover, optical emission spectroscopy (OES) showed atomic hydrogen radicals in the plasma phase, which likely causes deoxidation effect.