Dielectric properties in heteroepitaxial $Ba0.6Sr0.4TiO3$ thin films: Effect of internal stresses and dislocation-type defects Available to Purchase

A series of heteroepitaxial $Ba0.6Sr0.4TiO3$ were grown on $0.29(LaAlO3):0.35(Sr2TaAlO6)$ substrates using pulsed-laser deposition. X-ray characterization revealed compressive in-plane stresses in the thinnest films, which were relaxed in a continuous fashion with increasing thickness. A theoretical treatment of the misfit strain was in good agreement with the measured out-of-plane lattice parameter. The low-frequency dielectric constant was measured to be significantly less than the bulk value and found to decrease rapidly for films less than 100 nm. A thermodynamic model was developed to understand the reduction in dielectric constant. By observing the microstructure using plan-view and cross-section transmission electron microscopy, we identified local strain associated with a threading dislocation density on the order of $1011 cm−2$ as a possible mechanism for dielectric degradation in these films.