Ferroelectric properties of randomly oriented Bi1-xPrTi3O12 thin films fabricated by a sol-gel method

Praseodymium-substituted bismuth titanate, Bi3.6Pr0.6Ti3O12 (BPT), thin films were successfully fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by a sol-gel method. Fabricated BPT thin films were found to be random orientations, which were confirmed by X-ray diffraction experiment and scanning electron microscope analysis. The remanent polarization (2P(r)) and the coercive field of the BPT thin film annealed at 650 degrees C were 62 mu C/cm(2) and 205 kV/cm, respectively, at an applied electric field of 320 kV/cm. The measured 2P(r) of the randomly oriented BPT thin film is larger than those of Bi4-xLaxTi3O12 (x=0.75) and Bi4Ti3O12 thin films, and comparable with those of other lanthanide-substituted Bi4Ti3O12 thin films. The BPT thin film exhibits a good fatigue resistance up to 1.5x10(10) switching cycles at a frequency of 1 MHz with applied electric field of 120-240 kV/cm. These results indicate that the randomly oriented BPT thin film is a promising candidate among ferroelectric materials useful in lead-free nonvolatile ferroelectric random access memory applications. (c) 2005 Elsevier B.V. All rights reserved.