Degradation of the dielectric permittivity of a strongly oriented Ba0.25Sr0.75TiO3 layer by replacing a SrRuO3 electrode with an Ag one

Films of (Ba,Sr)TiO3 have been deposited with a quality allowing a ferroelectric Curie-Weiss behavior to be seen and a study of the influence of electrode material and interfaces in a capacitor. The measured value of the real part of the dielectric permittivity, epsilon('), of a 700 nm thick Ba0.25Sr0.75TiO3 layer decreased three times at temperatures around the Curie point, when one of the two SrRuO3 electrodes (the top one) was replaced with a silver one. This may be interpreted as if there were a series capacitance, C-s, at the ferroelectric-to-metal electrode. From the decreased epsilon('), C-s=1.2 muF/cm(2) was estimated for the Ag/Ba0.25Sr0.75TiO3 interface, corresponding to a characteristic length of about 2.6 Angstrom for the interface layer. (C) 2002 American Institute of Physics.