Lithium phosphorus oxynitride (LiPON) films were prepared by radio frequency magnetron sputtering. In order to control the atomic composition of the films, a mixture of Li3PO4 and Li2O powders was used as the sputtering target. The ionic conductivity of the films showed a maximum (6.4 x 10(-6) S/cm) when the molar ratio of Li3PO4 to Li2O in the target was 1:2. The films formed from a target not containing Li2O showed good durability in air at the expense of slightly poorer ionic conductivity. This is probably due to the amount of Li in the film being significantly less which effectively suppressed absorption of CO2 in air. (C) 2011 Elsevier B.V. All rights reserved.