EFFECT OF NONSTOICHIOMETRY ON DIELECTRIC-PROPERTIES OF STRONTIUM-TITANATE THIN-FILMS GROWN BY ARF EXCIMER-LASER ABLATION

Dielectric properties and lattice parameters of nonstoichiometric strontium titanate were systematically investigated. The X-ray diffraction measurements indicated the formation of SrO.(SrTiO3)n (n=4-53) instead of SrTiO3 with excess Sr. Epitaxial films grown on (111)Pt/(100)MgO by an ArF excimer laser ablation method were mostly orientated along the (102n + 1 underbar) axis, With decrease in the frequency of Sr-O plane sliding-in (increasing n value), the dielectric constant epsilon increased from 87epsilon0 to 300epsilon0. Furthermore, an improved property was also obtained in its temperature dependence. The sublattice (perovskite SrTiO3) in the vicinity of sliding-in Sr-O plane was slightly distorted (compressed by about 15%).