Gas pressures influence on the optical and mechanical properties of Ta2O5 films produced by reactive low voltage ion plating (RLVIP)

Ta2O5 films were deposited onto unheated glass substrates by reactive low v oltage ion plating (RLVIP). From the amorphous films with thicknesses betwe en 200 and 300 nm the optical properties (refractive index n, absorption co efficient k) and the mechanical properties (relative density rho and intrin sic stress sigma) were investigated in dependence on the relation between w orking gas pressure (Ar) and the reactive gas pressure (O-2). The films had k-values lower then 4 x 10(-4) at 550 nm at a gas pressure composition of 0.8 x 10(-3) mbar Ar and 2.0 x 10(-3) mbar O-2. With low total pressure hig h refractive indices, high compressive film stress and a high relative film density were found all decreasing with increasing gas pressure. A post dep osition heat treatment at 350 degrees C on air during 4 h resulted in a rem arkable decrease in the refractive index and the film stress. (C) 1999 Else vier Science S.A. All rights reserved.