Titanium oxynitride (TiNxOy) films were deposited on polyethylene terephthalate (PET) substrates by means of a reactive radio frequency (RF) magnetron sputtering system in which the power density was the varied parameter. Experimental results show that the deposited TiNxOy films with a thickness of about 55 nm have similar contents of TiN, TiNxOy and TiO2 bonds, although they are deposited at different power densities. The TiNxOy films deposited at a lower power density have fewer internal defects and grain boundaries and possess higher activation energy and a lower rate of water vapor and oxygen transmission through TiNxOy/PET films. (C) 2010 Elsevier B. V. All rights reserved.