Domain Engineering of Epitaxial PbTiO₃ Thin Films by the Control of Misfit Strain

Abstract

Ferroelectric domain structures and their evolution in the epitaxial PbTiO₃ thin films are greatly affected by the misfit strain and its relaxation during epitaxial film deposition on single crystalline MgO(001) substrates with epitaxial Pt electrode interlayer. The misfit strain could be controlled by varying the underlying interlayer thickness. As the thickness of Pt electrode decreases from 120 nm to 12 nm, the effective lattice constant of Pt electrode increases due to the suppressed generation of misfit dislocations at the Pt(001)/MgO(001) interface. Consequently, the compressive misfit strain in PbTiO₃ thin films decreases due to the decreased lattice mismatch with Pt electrode, which enhances the formation of 90° domains. Equilibrium domain structures in the epitaxial thin films are also analyzed by the finite element simulation and found to be consistent with the experimental observation. The results manifest that the domain structure and evolution of the epitaxial PbTiO₃ thin films could be engineered by the control of misfit strain.

Keywords:

• Ferroelectric thin films
• domain engineering
• Pt electrode thickness
• Finite element method

ACKNOWLEGEMENTS

This work was supported by the BK 21 Project, Korea. The experiments at the PLS was supported by the Ministry of Science and Technology (MOST) and POSCO, Pohang, Korea.