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, ε′, 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, Cs, at the ferroelectric-to-metal electrode. From the decreased ε′, Cs=1.2 μF/cm2 was estimated for the Ag/Ba0.25Sr0.75TiO3 interface, corresponding to a characteristic length of about 2.6 Å for the interface layer.