Characterization of Ta/sub 2/O/sub 5/-MgF/sub 2/ composite thin films

We deposited composite Ta/sub 2/O/sub 5/-MgF/sub 2/ thin films by coevaporation, and explored their optical and mechanical properties. The refractive indices of pure Ta/sub 2/O/sub 5/ and MgF/sub 2/ films were 1.94/spl sim/2.15 and 1.38 at 550 nm wavelength, respectively. In the composite film system, the measured refractive index agreed well with the Lorentz-Lorenz formula and all films had tensile stress, in the range (0.7/spl sim/3.1)/spl times/10/sup 9/ dyne/cm/sup 2/, depending upon the film composition. The film stress did not vary linearly with the film composition.