Composition, structure, and dielectric tunability of epitaxial SrTiO3 thinfilms grown by radio frequency magnetron sputtering

Epitaxial (001) oriented SrTiO3 films have been deposited on LaAlO3(001) su bstrates by off-axis radio frequency magnetron sputtering in Ar:O-2 gas mix tures at substrate temperatures ranging from 650 to 850 degrees C. For the deposition conditions used, stoichiometric targets yielded 20% Sr-deficient films, whereas Sr-enriched targets (Sr1.1TiO0.9O3.0) resulted in stoichiom etric films. The Sr-deficient films had a mosaic structure and a larger lat tice parameter in comparison to bulk SrTiO3. The stoichiometric films on th e other hand had a much higher crystalline quality in the as-deposited cond ition. The mosaicity of the latter films was primarily limited by the cryst alline quality of the LaAlO3 substrates. The lattice parameters of the stoi chiometric films were also smaller than the Sr-deficient ones and closer to the bulk value. The dielectric properties of the stoichiometric films were superior to the Sr-deficient films. For films with a thickness of similar to 300 nm, the typical dielectric constants as measured at similar to 77 K and I MHz were determined to be 820 and 500, for the stoichiometric and Sr- deficient films, respectively. Also the capacitance change, as a direct cur rent bias voltage was applied to an interdigital capacitor, was higher for the stoichiometric film, 27.3% as compared to 8.6% when applying a bias of 300 V at 77 K. We also demonstrate the effectiveness of thermal annealing i n improving both crystalline quality and dielectric properties, especially for the Sr-deficient films. (C) 1999 American Vacuum Society. [S0734-2101(9 9)010002-7].