X-RAY DIFFRACTION STUDY OF THE DOMAIN STRUCTURE AND ITS STABILITY IN PbTiO₃ THIN FILMS GROWN ON MgO(001) BY MOCVD* B.-M. Yen, R.S. Batzer, Haydn Chen, Department of Materials Science & Engineering, University of Illinois, Urbana, IL 61801

Lead Titanate (PT) and Lead Zirconium Titanate (PZT) have generated much interest in electrical and optical industries due to their desirable piezoelectric, ferroelectric and electro-optic properties. Recently, as thin film processing becomes more refined, research and development of PT and PZT materials in the form of thin films have become increasingly active. Several different fabrication methods have been utilized to grow epitaxial PT and PZT films including the MOCVD technique employed by the authors. The purpose of this study is twofold: first, to observe the domain structure evolution of MOCVD-grown epitaxial PT films on MgO(001) substrate during heating to temperatures above and below the Curie point (~490deg.C); and second, to cycle the temperature in order to study the stability of the domain configuration. The significance of this work lies in the assessment of reproducibility of ferroelectric domain configuration due to thermal cycling. This work was performed using a four-circle x-ray diffractometer in situ with a miniature hot stage. Rocking curves were used to monitor the domain evolution. Lattice constants were measured at various temperature to determine the ferroelectric transition temperatures (Curie point) during heating and cooling. The Curie temperatures in the geometrically confined PT thin films were found to be lower than the bulk value. A model concerning the film stress effect on the total free energy is proposed to explain this effect.

* Research support by the US Department of Energy.