Microstructure and growth mode at early growth stage of laser-ablated epitaxial Pb(Zr0.52Ti0.48)O3 films on a SrTiO3 substrate

Abstract

The surface morphology and microstructure of laser-ablated Pb(Zr0.52Ti0.48)O3 (PZT) films on a (100) SrTiO3 (STO) substrate at early growth stage are characterized by means of atomic-force microscope, x-ray diffraction, and high-resolution transmission electron microscopy analysis. The (100) STO surface is found to be very favorable for epitaxial growth of (001) PZT films, which undergo a three-dimensional island growth mode. We observed a two-layer structure at the film thickness around 40–50 nm when small nuclei/grains merge into large grains. With further increase of film thickness, a column-like growth mode dominates the film crystalline structure, which results in an almost independent in-plain grain size of 100–150 nm with increasing film thickness and a limited film roughness. A very sharp interface between the PZT thin film and STO substrate is observed. The PZT film shows a perfect stacking lattice at a thickness of around 20 nm and above, indicating that the misalignment due to the interface stress and defects is healed after stacking about 50 ML of the film. These results have shed some light on the growth mechanism of epitaxial PZT film on YBCO or other bottom layers for microelectromechanical systems application.