Composition/structure/property relations of multi-ion-beam reactive sputtered lead lanthanum titanate thin films: Part II. Textured microstructure development

Abstract

This paper, the second of three parts, presents a detailed analysis of the crystallographic texture observed in lead lanthanum titanate (PLT) thin films deposited by multi-ion-beam reactive sputtering. Since films were deposited at a substrate temperature of 100 °C, they exhibit an amorphous structure that can be described by the structure zone model. The as-deposited microstructure is transformed via crystallization of the perovskite phase and PbO evaporation during postdeposition annealing. Transmission electron microscopy was used to determine that phase pure PLT films develop textured clusters (as large as 700 nm in diameter) consisting of 〈100〉 aligned 10 nm nanocrystals. As excess PbO is added to the PLT film, the textured cluster size decreases until only isolated PLT nanocrystals exist. Below a critical quantity of excess PbO in the as-deposited film (approximately 15 mole%), the textured cluster structure produces a 〈100〉 texture through the film thickness, which generates x-ray diffraction patterns typical of textured microstructures. At high PbO contents, the excess PbO causes the formation of clusters that are smaller than the film thickness, resulting in a polycrystalline-type x-ray diffraction pattern. A qualitative model describing microstructure development is presented.