J Phys Condens Matter. 2010 Sep 08;22(35):355901. doi: 10.1088/0953-8984/22/35/355901. Epub 2010 Aug 13.

First-principles study on ferroelectricity at PbTiO3 surface steps.

Journal of physics. Condensed matter : an Institute of Physics journal

T Shimada, S Tomoda, T Kitamura

PMID: 21403300 DOI: 10.1088/0953-8984/22/35/355901

Abstract

We performed ab initio density functional theory calculations to investigate ferroelectricity at PbTiO(3) surface steps consisting of (100) and (001) surfaces with the polar axis in the [010] direction. Ferroelectricity was enhanced at PbO-terminated surface steps due to enhanced covalent Pb-O bonding because of the low coordination number of Pb atoms at the step edge. In contrast, ferroelectric distortions were suppressed at TiO(2)-terminations, because of electron transfer from Pb-O sites to Ti-O sites. Spontaneous polarization at the surface step increased when tensile strain was applied in the [010] direction and decreased when compressive strain was applied. At a critical compressive strain, the polarization direction changed and a polydomain structure was formed that consisted of 90° and 180° domain walls aligned with the surface step edge. This polydomain structure compensates surface charges that would generate a depolarizing field, thereby stabilizing ferroelectric distortions at the surface step. The polydomain structure also explains the formation mechanism of the experimentally observed 180° domain wall pinned at the surface step edge.

Publication Types

• Journal Article
• Research Support, Non-U.S. Gov't