DIELECTRIC-PROPERTIES OF SPUTTERED SRTIO3 FILMS

The dielectric properties of [100]-oriented epitaxial SrTiO3 films as used in high-T(c) heterostructures have been studied as a function of temperature and applied electric field by using in situ grown heterostructures (Mg/SrTiO3/SrTiO3:Nb and Au/YBa2Cu3O7-x/SrTiO3/SrTiO3:Nb). The dielectric behavior of these films is characterized by a rather low sample capacitance as compared to bulk single-crystal values and by occurrences of maxima in the capacitance-voltage and capacitance-temperature curves. The maximum attainable polarization was found to be 80 mC/m2 at 4.2 K. Complementary measurements on single crystals of SrTiO3 and SrTiO3:Nb reveal that the behavior of these SrTiO3 thin films can be understood from the bulk properties with additional strong charge trapping at the film-substrate interface.