Epitaxial growth of PbZr0.5Ti0.5O3 thin films on (001) LaAlO3 by the chemical solution deposition method

Abstract

Epitaxial PbZr0.5Ti0.5O3 (PZT) thin films were grown on (001) LaAlO3 substrates (∼6.1% lattice mismatch) by the chemical solution deposition method. The sequence of epitaxy during heating between 375 and 700 °C/1h was characterized by x-ray diffraction and transmission electron microscopy. At approximately 375 °C/1h, a nanocrystalline metastable fluorite phase of PZT was formed from the pyrolyzed amorphous precursor. At higher temperatures (400–425 °C/1h), thermodynamically stable PZT crystallites were first observed at the interface; with increasing higher temperatures, these nuclei grew across the interface and through the film toward the surface by consuming the metastable nanocrystalline fluorite grains. PZT thin films annealed above ∼500 °C/1h were observed to be dense with an epitaxial orientation relationship of [100](001)PZT‖[100](001)LAO. The metastable nanocrystalline fluorite to the stable single-crystal perovskite transformation gives an extra driving force by providing an additional decrease in free energy in addition to a driving force from the elimination of grain boundary area for epitaxy.