Deterministic domain formation observed in ferroelectrics by electrostatic force microscopy

Abstract

The effect of crystalline defects on the formation of ferroelectric domains in triglycine sulfate (TGS) crystals has been investigated using a dynamic contact electrostatic force microscopy. This detection method, based on the Coulomb interaction between the charge on the tip and the surface charge on the sample, yields a good spatial resolution as well as a complete separation between the topography and the domain image. The crystal imperfections, degraded surface, and strain in the crystal affect strongly the static domain configuration. Comparison of the topography to the domain image reveals a deterministic behavior in the formation of the equilibrium domain configuration, which is determined by twin boundaries in the crystal. Surface imperfections appear different depending on the polarization direction. Positively polarized regions show circular islands, whereas negatively polarized region shows circular holes as well as islands of various shapes. When TGS samples were cooled below the Curie temperature from a paraelectric state, the relaxation rate of the domains from the nonequilibrium configuration to the equilibrium configuration is substantially decreased forthe sample that contains many defects, indicating a pinning effect by the crystal imperfections such as the degraded surface and stress in the crystal.