Effect of sorbed water on the electrical resistance of polysodium phosphate thin films

Measurements have been made of complex impedance and sorbed water of polysodium phosphate. The resistance and its activation energy decreases with an increase in the amount of sorbed water. The amount of sorbed water is strongly affected by the Na₂O/P₂O₅ mol ratio. The humidity dependence of the activation energy and the resistance is lowered by decreasing the average chain length of polysodium phosphate. This results in an increase in the amount of sorbed water. Especially, in low humidity conditions, the decrease in the resistance and the activation energy are achieved by increasing the concentration of the strongly acidic PO-H group. These improvements can not be achieved by increasing the Na₂O/P₂O₅ mol ratio. In a humid atmosphere, the resistance of the film, in which the Na₂O/P₂O₅ mol ratio is less than 0.8, is inversely proportional to the concentration of the strongly acidic PO-H group.