Dependence of electrical properties on film thickness in lanthanum-doped lead zirconate titanate stannate antiferroelectric thin films

Lanthanum-doped lead zirconate titanate stannate antiferroelectric thin films with compositions in antiferroelectric orthorhombic region have been prepared on Pt-buffered Si substrates by the sol-gel method, with the film thickness from 0.1 to 1.0 mu m. The dependence of dielectric and ferroelectric properties on film thickness have been studied, with the emphasis on field-induced phase switching. The dielectric constant and maximum polarization decrease with the reduction of film thickness, which are similar to ferroelectric thin films. However, the decrease of film thickness also leads to the decrease of the phase switching fields, the appearance of remanent polarization in the hysteresis loops, and the smearing of antiferroelectric-ferroelectric phase switching. These phenomena are believed to be caused mainly by the stress effect between the film and substrate. Due to thermal mismatch, the films are under high tensile stress after annealing, and the stress effect becomes more significant with the decrease of film thickness. This makes the thinner films more preferable to the ferroelectric phase and causes the retention of ferroelectric phase in the films with thickness less than 0.4 mu m. (C) 1999 American Institute of Physics. [S0021-8979(99)03707-X].