Ferroelectric hysteresis loops of (Pb,Ca)TiO3 thin films under spherical indentation

Ferroelectric switching under indentation forces has been studied for a set of (Pb,Ca)TiO3 ferroelectric thin films. A radius of contact of 10.2 mum and an average pressure of 1.5 GPa have been estimated by Hertzian theory. The indentation stress field prevents the ferroelectric hysteresis loops from becoming saturated. Ferroelectric switching is hindered and apparent coercive fields as high as 400 kV cm(-1) were observed. As a consequence, small remnant polarizations were obtained. The effect is proposed to be caused by a combination of a decrease of the electric polarization that can be switched by 180degrees domain wall movements, as a consequence of stress induced 90degrees domain wall movements under the indentation force, and the clamping of the 90degrees domain walls by the indentation stress field. (C) 2004 American Institute of Physics.