Enhanced dielectric properties of Ba_(1-x)Sr_(x)TiO_(3) thin film grown on La_(1-x)Sr_(x)MnO_(3) bottom layer

摘要

The Ba_(0.7)Sr_(0.3)TiO_(3) (BST)/La_(0.67)Sr_(0.33)MnO_(3) (LSMO) heterostructure has been fabricated by pulsed-laser deposition on (001) SrTiO_(3) single crystal substrate. The crystallization and surface morphology of the heterostructure have been characterized by x-ray diffraction and atomic force microscopy. The composition distribution along the depth of the heterostructure is analyzed by Auger electron spectroscopy. It is founded that the LSMO bottom layer shows a marked effect on the dielectric properties of the BST films. Comparing with BST/YBCO (YBCO—YBa_(2)Cu_(3)O_(7)) heterostructure grown by similar process, the dielectric loss exhibits much lower and less frequency dispersive, especially in the high frequency region. The loss tangent at 100 kHz is about 0.012 and the figure of merit factor is about 25 under the condition of 200 kV/cm. Ferroelectric hysteresis measurement shows that the remanent polarization and coercive field of the heterostructure are 3.4 μC/cm~(2) and 39 kV/cm, respectively. These parameters are all better than BST/YBCO heterostructure. The good surface morphology and the element diffusion between BST and LSMO layers may be suggested to be responsible for the above-improved parameters of BST/LSMO heterostructure.