Effect of interfaces on the dielectric response of a SrTi O3 layer between metallic oxide electrodes
Journal article, 2006
The temperature dependence of the dielectric permittivity ε of an 800 nm thick SrTi O3 layer in epitaxial SrRu O3 SrTi O3 SrRu O3 and Y Ba2 Cu3 O7-δ SrTi O3 SrRu O3 heterostructures followed the relation ε-1 = ε0 -1 C0 -1 (T- TCW) + εI -1, where C0 and TCW are the Curie constant and the Curie-Weiss temperature for the strontium titanate bulk crystal, respectively. The effective dielectric constant is lower than the bulk value due to the interfaces of the SrTi O3 film to its electrodes as given by εI. The εI was diminished roughly 2.5 times when the top SrRu O3 electrode in the trilayer was replaced by one of Y Ba2 Cu3 O7-δ. The capacitances Ci per unit area of the SrRu O3 SrTi O3 and Y Ba2 Cu3 O7-δ SrTi O3 interfaces were 8.2 and 2.3 F cm2, respectively. Characteristic penetration depths L of the electric field into the SrRu O3 and Y Ba2 Cu3 O7-δ electrodes were extracted from the Ci s and are several times larger than corresponding data estimated from free electron type models of metals. A diminished charge carrier density in the electrode very close to the interface is a likely reason for the enhanced L. © 2006 The American Physical Society.