REDUCTIVE CORROSION OF ITO IN CONTACT WITH AL IN ALKALINE-SOLUTIONS

Tin-doped indium oxide (ITO) layers show severe corrosion in alkaline solutions when they are in electrical contact with Al. This corrosion process is investigated by etching experiments, electrochemical measurements, and analytical techniques. It is shown that Al maintains ITO at a cathodic potential where it is reduced. Al itself is oxidized and dissolves as AlO2-. The products of the ITO corrosion are most probably SnO3(2-), which dissolves in the solution, and In metal, which forms grains at the surface. This causes a gray opaque appearance and a disconnection between the ITO and Al. When there is no longer electrical contact, the Al dissolution proceeds but the ITO attack is found to stop.