Crystalline and electrical properties of ( Bi , La ) Ti O thin films coated on 3 12 Al O y Si substrates 2 3

Bi La Ti O (BLT, xs0.67–0.70) ferroelectric thin films were prepared on a single crystalline aluminum oxide film onto 4yx x 3.0 12 Si substrate (c-Al O ySi), and amorphous phase aluminum oxide film onto Si substrates (a-Al O ySi) by the sol–gel method. In 2 3 2 3 order for crystallization, the as-coated films were annealed at the temperature of 650 and 700 8C for 30 min. The crystalline quality, surface morphologies and electrical properties were affected by the substrate types as well as the annealing temperature. The BLT films annealed at above 650 8C exhibited typical bismuth layered perovskite structures with (00l) preferred orientation. From X-ray diffraction analyses, the BLT films coated on c-Al O ySi substrate were higher in reflection peaks and smaller in full 2 3 width at half maximum (FWHM) values compared with the ones coated on a-Al O ySi substrate. The R value of the film 2 3 rms annealed at 700 8C on c-Al O ySi substrates was three times smaller than that of the film coated on a-Al O ySi substrate, 2 3 2 3 showing a rather smooth surface when it was coated on c-Al O ySi substrate. The memory window voltage of the BLT film 2 3 coated on c-Al O ySi substrate was 2.5 V, which is about twice compared with the one coated on a-Al O ySi substrate. The 2 3 2 3 leakage current of BLT film annealed at 650 8C was approximately 1=10 Aycm at the applied voltage of 3 V for both y7 2 samples. 2003 Elsevier B.V. All rights reserved.