Microstructure and dielectric properties of Ba_1-xSr_xTiO₃ films grown on LaAlO₃ substrates

We report a systematic study of the microstructure and dielectric properties of barium strontium titanate, Ba_1-xSr_xTiO₃, films grown by laser ablation on LaAlO₃ substrates, where x=0.1-0.9 at an interval of 0.1. X-ray diffraction analysis shows that when x<0.4, the longest unit-cell axis is parallel to the plane of the substrate but perpendicular as x approaches 1. Dielectric constant versus temperature measurements show that the relative dielectric constant has a maximum value and that the peak temperatures corresponding to the maximum relative dielectric constant are about 70°C higher when x≤0.4 but similar when x>0.4, compared with the peak temperatures of the bulk Ba_1-xSr_xTiO₃. At room temperature, the dielectric constant and tunability are relatively high when x≤0.4 but start to decrease rapidly as x increases.