Internal residual stress studies and enhanced dielectric properties in La0.7 Sr0.3 CoO3 buffered (Ba,Sr) TiO3 thin films

Ba0.6 Sr0.4 TiO3 (BST) thin films were deposited on La0.7 Sr0.3 CoO3 (LSCO) buffered and unbuffered Pt (111)/Ti/ SiO2 /Si substrates by pulsed laser deposition. The former exhibits a (100) preferred orientation and the latter a random orientation, respectively. Grazing incident x-ray diffraction study revealed that the tensile residual stress observed in the latter is markedly reduced in the former. As a result, the dielectric property of the LSCO buffered BST thin film is greatly improved, which shows a larger dielectric constant and tunability, smaller loss tangent, and lower leakage current than those of the unbuffered BST thin film. The relaxation of the larger tensile residual stress is attributed to the larger grain size in the buffered BST thin film and to a closer match of thermal expansion coefficient between the BST and the LSCO buffer layer. © 2009 American Institute of Physics.