Charge transfer by contact between metallic samples and insulating coatings

The paper deals with experiments carried out in ambient air to study charge transfer in a quasi equilibrium state from metallic samples into insulating layers covering their surface. Experimental results concern the surface potential variations undergone when the thickness of these layers is increased. They show that below a critical thickness xcrit depending on the layers nature, the electrical behaviour of the layers is governed by a surface charge, and that beyond this thickness value, it becomes space charge dominated. A model fitting with these results is proposed.