Dielectric relaxation and charge transport mechanisms in (Ba,Sr)TiO₃ thin films

Electrical properties of barium strontium titanate (BST) thin films were investigated. The transient relaxation current was measured at various temperatures for different BST thicknesses and was found to obey the Curie-von-Schweidler law. A bulk related relaxation model involving hopping of charge carriers was used to explain these results. In addition, the frequency dependence of the dielectric loss was measured and compared with the transient relaxation current. To interpret the leakage data, the temperature and field dependence were analyzed qualitatively and quantitatively. An interfacial layer with reduced static dielectric constant enhances the electric field near the electrodes. For temperatures lower than 400 K and electric fields higher than 3 MVcm−1 charge transport is dominated by Fowler-Nordheim tunneling.