Microstructure and dielectric properties of Ba1-xSrxTiO3 films grown on LaAlO3 substrates

We report a systematic study of the microstructure and dielectric propertie s of barium strontium titanate, Ba1-xSrxTiO3, films grown by laser ablation on LaAlO3 substrates, where x=0.1-0.9 at an interval of 0.1. X-ray diffrac tion analysis shows that when x < 0.4, the longest unit-cell axis is parall el to the plane of the substrate but perpendicular as x approaches 1. Diele ctric constant versus temperature measurements show that the relative diele ctric constant has a maximum value and that the peak temperatures correspon ding to the maximum relative dielectric constant are about 70 degrees C hig her when x less than or equal to 0.4 but similar when x > 0.4, compared wit h the peak temperatures of the bulk Ba1-xSrxTiO3. At room temperature, the dielectric constant and tunability are relatively high when x less than or equal to 0.4 but start to decrease rapidly as x increases. (C) 2000 America n Institute of Physics. [S0003-6951(00)01534-5].