Impact of the top-electrode material on the permittivity of single-crystalline Ba0.7Sr0.3TiO3 thin films

We observed significant influence of the top-electrode material on the thickness and temperature dependences of the dielectric response of single-crystalline Ba0.7Sr0.3TiO3 thin-film capacitors. For SrRuO3/Ba0.7Sr0.3TiO3/SrRuO3 samples, the position of dielectric maximum shifts to lower temperatures with decreasing film thickness, whereas the samples with Pt top electrodes exhibit an opposite trend. Moreover, the apparent "interfacial" capacitance, extracted from the film-thickness dependence of dielectric response, is very different for these two types of samples and strongly depends on temperature. Experimental results are analyzed theoretically in light of the depolarizing-field and strain effects on the transition temperature and permittivity of ferroelectric films. (c) 2005 American Institute of Physics