DEPOSITION OF AMORPHOUS BATIO3 OPTICAL FILMS AT LOW-TEMPERATURE

A reactive partially ionized beam technique has been used to deposit a morphous BaTiO3 films at room temperature. The procedure employing ind ependently controlled evaporation and ionization of Ba and TiO has bee n optimized to produce highly transparent films. Films deposited on qu artz or glass show 100% optical transmission over the visible waveleng ths with respect to the substrate. The refractive index can be varied over a range of 1.9-2.0 by varying the Ba/Ti ratio without effecting t he optical transparency. Films with refractive indices up to 2.4 can b e deposited but the optical transmission decreases. The best optical p roperties are obtained for films with near stoichiometric Ba/Ti ratio. Annealing at temperatures less than 500-degrees-C leads to densificat ion of the films with a 2%-3% decrease in film thickness. The anneal i ncreases the refractive index marginally. The optical band gap of the films was calculated from the experimental transmission plots. The E(g ) value of 4.6 +/- 0.1 eV for stoichiometric films decreases to 4.3 eV for nonstoichiometric films.