Microstructural Model on the Evolution of Domain Structure during Processing of PbTiO 3 Thin Films on MgO(100) Substrates

A two‐dimensional microstructural model is proposed to explain the origin of the 90° domain structure of epitaxial PbTiO 3 thin films grown on MgO(100) substrates by radio frequency sputter deposition. During film deposition at or above 600°C, the film grows epitaxially in a cubic phase without any domain structure. At or just below the Curie temperature, the film mainly consists of α‐domains with a small portion of c ‐domains nucleated in a triangular shape. The c ‐domains gradually expand with decresasing temperature to relax the strain energy caused by the difference in thermal contraction rate between the c ‐axis of α‐domains and the substrate, forming consequently thin strips of α‐domains distributed in the matrix of c ‐domains at room temperature.