Microstructure and dielectric properties of textured SrTiO 3 thin films

Abstract

We investigate the relationship between microstructure and dielectric properties of textured SrTiO 3 thin films deposited by radio-frequency magnetron sputtering on epitaxial Pt electrodes on sapphire substrates. The microstructures of Pt electrodes and SrTiO 3 films are studied by transmission electron microscopy, atomic force microscopy, and X-ray diffraction. SrTiO 3 films grown on as-deposited and annealed Pt electrodes, respectively, consist of a mixture of (111)- and (HO)-oriented grains. Temperature-dependent dielectric measurements show that differences in texture and microstructure are reflected in the Curie-Weiss behavior of the SrTiO 3 films. Phenomenological models that account for the effects of thermal mismatch strain on the dielectric behavior are developed for different film textures. The models predict that at a given temperature, paraelectric (111)-oriented films of SrTiO 3 on tensile substrates will have a higher Curie-Weiss temperature and a greater dielectric constant than (110)-oriented films or bulk SrTiO 3. The experimental dielectric behavior is compared with the predictions from theory, and different contributions, such as interfacial layers, film stress, and microstructure, to the Curie-Weiss behavior are discussed.