This work presents an investigation of the role of the nitrogen flow rate on the composition, structure and ionic conductivity of thin films prepared by reactive radio-frequency (rf) sputtering of lithium metaborate targets. It was found that sputtering at constant nitrogen pressure but with increasing nitrogen flow rate leads to thin films with significantly increased nitrogen content. The effect of nitridation on the borate network has been studied by infrared transmittance spectroscopy and revealed boron-nitrogen bonding in triangular arrangements of the glass network, followed by a parallel destruction of borate tetrahedral units. The ionic conductivity of thin films was also measured and found to increase with the nitrogen amount in the film. (c) 2008 Elsevier B.V. All rights reserved.