The optical properties and residual stress of tantalum pentaoxide (Ta2O5) thin films prepared by ion beam sputtering deposition was investigated experimentally as a function of sputtering ejection angle. Thin films were deposited on unheated BK7 glass substrates and silicon wafers at different positions relatively to a metal target, which corresponds to different ejection angles. The optical constants, film thickness, refractive index and extinction coefficients, of the Ta2O5 films were shown to be influenced by the ejection angle. The residual stresses in sputtering Ta2O5 thin films were also found to vary with the ejection angle. All deposited films were amorphous as measured by the X-ray diffraction method. The surface morphology and microstructure of thin films were analyzed by atomic force microscopy and scanning electron microscopy. (C) 2008 Elsevier B.V. All rights reserved.