Characteristics of Ba_xSr_(l-x)TiO_3 thin films grown by pulsed laser ablation of rotating split targets of BaTiO_3 and SrTiO_3

摘要

We have grown heterostructures of Ba_xSr_(l-x)TiO_3 (BST)/La_(0.7)Sr_(0.3)MnO_3(LSMO) on LaAlO_3(LAO) substrates by the pulsed laser deposition method. BST films with x = 0.2, 0.5, 0.7 and 0.8 have been prepared using a novel rotating split-target arrangement. The lattice constant of the BST films is found to vary linearly with Ba/Sr ratio. An excellent cube-on-cube epitaxial relationship of (100)_(BST)||(100)_(LSMO)||(100)_(LAO) has also been obtained. Scanning electron microscopy studies have revealed smooth and crack-free BST films with a uniform grain size of about 100 nm. Dielectric measurements, made with patterned Au top electrodes and conducting LSMO bottom layers, have shown a maximum permittivity of approximately 280 at 5 kHz in BST films with x = 0.7. P-E loop analyses of the Ba_(0.7)Sr_(0.3)TiO_3 and Ba_(0.8)Sr_(0.2)TiO_3 films have yielded remnant polarization values of 1.66 and 1.81 μC/cm~2, respectively.