Characterizations of (Bi,La)Ti3O12 thin films coated on a single-crystalline Al2O3 insulation layer/Si substrate

Bi4-xLaxTi3.0O12 (BLT, x = 0.67 - 0.70) ferroelectric thin films were prepared on a single crystalline aluminum oxide film/Si substrate (c-Al2O3/Si) by using the sol-gel method. In order to crystallize the as-coated films, they were annealed at temperatures of 650 .deg. C and 700 .deg. C for 30 min. The crystallinity, the surface morphologies, and the electrical properties were affected by the annealing temperature. The BLT films annealed at above 650 .deg. C exhibited typical bismuth layered perovskite structures with (00l) preferred orientations. From the Auger electron spectroscopy, there was no significant inter-diffusion through the interface between the BLT film and c-Al2O3 insulation layer. The window voltage increased from 1.3 V to 2.5 V with increasing annealing temperature from 650 .deg. C to 700 .deg. C at an applied bias voltage of 5 V. The leakage current of the BLT films annealed at 650 .deg. C was about 8 x 10-8 A/cm2 at 3 V.