Surface chemistry induced by air corona discharges in a negative glow regime

This paper deals with oxidation phenomena observed on surfaces submitted to the action of corona-activated ambient air. The study was mainly performed with gold and silicon surfaces chosen for their great material stability. During the discharge, the surfaces become covered with micronic water droplets which look like granules. They grow in number with the duration of the sample exposure to the discharge, their mean size depending on the material, and they resist the vacuum of the electron scanning microscope, but not its electron beam, especially when it is focused on them. From a chemical point of view, the surfaces are now oxidized in a way comparable with what can be obtained in liquid electrochemical solutions and, apart from the electrode material oxides or hydroxides observed, one can also find nitrogen oxides, but in clearly smaller quantities.