Stress Induced Depolarisation of Ferroelectrics in Thin Film Form

Depolarisation occurs in ferroelectric thin films during their indentation with spheres. This depolarisation can be inhomogenous under the area of contact along the radial direction, as a consequence of the stress gradient along that direction. Depolarisation occurs in tetragonal structure lanthanum modified lead titanate films without any significant dependence on the orientation of the 90° domain walls with respect to the indentation axis. This suggests that non-180° wall movements may not be directly responsible for the phenomenon. Depolarisation also occurs in lead zirconate titanate films with the tetragonal structure and at the rhombohedral-tetragonal morphotropic phase boundary. Possible alternative mechanisms to non-180° domain wall movements are discussed.

Keywords:

• Ferroelectric Films
• Stress Induced Depolarisation
• Nanoindentation
• Spherical Indenters