Samples of Sr-deficient and stoichiometric epitaxial (001) film, deposited onto (110)rhombohedral LaAlO3 substrates by means of radio-frequency magnetron sputtering, were characterized by using high-resolution transmission electron microscopy. Subsequent heat treatment in O had a positive effect upon the dielectric properties. The Sr-deficiency had a large negative effect upon the microwave dielectric constant of the films. These changes were related to changes in lattice parameter. Misfit dislocations were present at the film/substrate interface of all of the samples. The residual elastic strain compressed the SrTiO3 unit cell in the substrate surface plane, and expanded it by an equal amount in the [001] direction. The use of X-ray diffraction revealed that a tetragonal distortion due to mismatch strain was restricted to the narrow region which was closest to the film/substrate interface.

L.Ryen, E.Olsson, L.D.Madsen, X.Wang, C.N.L.Edvardsson, S.N.Jacobsen, U.Helmersson, S.Rudner, L.D.Wernlund: Journal of Applied Physics, 1998, 83[9], 4884-90