Effects of substrate condition on calcium corrosion and its role in the calcium test for water vapour transmission rate

The electrical Ca test is a standard method for the estimation of the water vapour transmission rate through the encapsulation barriers. Here, we discuss the corrosion process of thin Ca films under different preparation conditions, and the impact of the substrate temperature. It is demonstrated that without vacuum drying of substrate, the Ca films corrode from the substrate side, even though they are encapsulated. The thickness dependence revealed its influence on lifetime, but not on its electrical properties. These observations reveal the strong impact of the Ca fabrication technology and measurement procedure on the corrosion process of Ca thin films.