Improved ferroelectric properties of Cr-doped Ba0.7Sr0.3TiO3 thin films prepared by wet chemical deposition

Ferroelectric Ba0.7Sr0.3TiO3 (BST) thin films with/without Cr-dopant have been fabricated on Pt(111)/Ti/SiO2/Si(100) substrates using wet chemical deposition. From atomic force microscope analysis, it has been found that the average grain sizes of the films increase from 10.7 to 29.2 nm with increasing Cr content from 0 to 5 mol%. Dielectric constant tunability of the 5 mol% Cr-doped BST thin film has been measured to be 56.1% with a dc bias field of 267 kV/cm, which is larger than 26.3% for the undoped BST thin film. Furthermore, the 5 mol% Cr-doped BST film exhibits hysteresis characteristics with the remanent polarization (2Pr) of 6 μC/cm2 and the coercive field (2Ec) of 40 kV/cm with a dc bias field of 230 kV/cm. The leakage current densities of the Cr-doped BST thin films are approximately 1 order of magnitude lower than that of the undoped BST thin film. The improved ferroelectric properties were attributed to the increased grain size and defect dipoles in the BST film by means of acceptor (Cr) doping.