High nonlinearity of Ba0.6Sr0.4TiO3 films heteroepitaxially grown on MgO substrates

We have heteroepitaxially deposited Ba0.6Sr0.4TiO3 (BST) thin films on (001 )-oriented MgO substrates using pulsed-laser deposition. By optimizing the deposition temperature and adjusting the film thickness, we have successful ly increased the dielectric nonlinearity and decreased the dielectric loss of BST films. BST thin films grown at 750 degrees C with a thickness of 1.1 mu m showed a dielectric constant tunability of greater than 65% and a tun ability/loss of 43 at a surface electric field of 80 kV/cm at room temperat ure. X-ray diffraction and transmission electron microscopy analyses indica ted that the tunability and dielectric loss were closely related to the cry stallinity of the BST films. (C) 2000 American Institute of Physics. [S0003 -6951(00)00742-7].