Microstructure-dependent dielectric properties of TbMnO3 in Au/TbMnO3/YBa2Cu3O7-x capacitors

Au/TbMnO3(TMO)/YBa2Cu3O7-x (YBCO) capacitors were fabricated on LaAlO3 (LAO) and SrTiO3 (STO) substrates under identical conditions. Dielectric properties were measured in the temperature range from 20 to 350 K. High dielectric constants and single dielectric transition peaks were found in both TMO films. The dielectric constants of TMO film on STO substrate were larger than those of TMO film on LAO substrate; correspondingly, the transition temperature of TMO film on STO substrate was higher than that of TMO film on LAO substrate. Although x-ray diffraction showed both TMO films had the same epitaxial orientation, atom force microscopy revealed that the films had different surface morphologies, which originated from the YBCO layers on different substrates. The good surface morphology of YBCO layer and the element diffusion between TMO and YBCO layers may be suggested to be responsible for the significant improvement in the dielectric properties of TMO thin film. (c) 2006 American Institute of Physics.