Effect of in-plane tensile strain in (100)/(001)-oriented epitaxial PbTiO_3 films on their phase transition temperature and tetragonal distortion

摘要

(100)/(001)-oriented epitaxial lead titanate (PbTiO_3) films with various thicknesses were grown on (100) KTaO_3 substrates by pulsed metal-organic chemical vapor deposition. The change of crystal structure with film thickness and deposition temperature was investigated. The paraelectric phase of 50 and 100nm-thick films had a tensile strain of 0.5% and almost 0% at 700 °C, respectively. The phase change temperature from the paraelectric phase to the ferroelectric phase, the Curie temperature (Tc), increased with the in-plane strain of the paraelectric phase; that is, 7c increased with decreasing film thickness. In contrast, room-temperature tetragonal distortion decreased as the film became thinner. This study reveals the effect of in-plane tensile strain in (100)/(001)-oriented epitaxial PbTiO_3 films with higher Tc and smaller tetragonal distortion at room temperature.