The optical properties and intrinsic stress of TA(2)O(5) thin films deposited by dual ion beam sputtering (DIBS) were studied as a function of the assist ion beam voltage (250-650 V). When the assist ion beam voltage was in the range of 350-450 V, the transmittance at the quarter-wave point reached its highest value (lowest absorption). The refractive index increased to 2.185 as the assist ion beam voltage increased from 250 to 350 V, but decreased as the assist ion beam voltage was further increased from 350 to 650 V. (c) 2007 Elsevier B.V. All rights reserved.