Synthesis and dielectric characteristic of Ba1−xSrxTiO3 thin films-based strontium-barium alkoxides derivatives

Homogeneous Ba1−xSrxTiO3 (BST) sols have been synthesized using barium, strontium acetate, and titanium tetra-n-butoxide as starting materials. Acetic acid and ethylene glycol were selected as solvents. The formamide was selected as an additive to adjust the solution viscosity in order to reduce the crack of the BST thin films. The structure and thermal decomposition process of BST gel powders and thin films, which were prepared from a precursor of strontium-barium titanate alkoxides, were investigated by means of differential thermal/thermogravimetric analyses (DTA/TGA) and X-ray diffraction measurements. DTA/TGA technique was used to determine the temperature of decomposition and crystallization. The BST thin films were prepared by a spin-on sol–gel process on Pt/Ti/SiO2/Si (1 0 0) substrates. The thin films were crystallized above 600°C, and formed completed perovskite structure around 700°C. The capacitance–voltage curve shows that the polarization and capacitance vary non-linearly with an applied field due to the domain structure. A tunability of dielectric constant about 29.3% and a figure of merit, K=6.5, were obtained with an electric field of 150 kV cm−1.