Tailoring the microstructure and dielectric properties of Ba0.5Sr0.5TiO3 thin films by solution-based processing in the frame of the Microstructural Zone Model

• Published in: Journal of alloys and compounds Vol. 743; pp. 812 - 818
• Main Authors: Pečnik, Tanja, Benčan, Andreja, Glinšek, Sebastjan, Malič, Barbara
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.04.2018
• Subjects: Chemical solution deposition; Dielectric properties; Ferroelectric thin films; Microstructural Zone Model; Microstructure; Microstructural Zone Model; Chemical solution deposition; Microstructure; Dielectric properties; Ferroelectric thin films
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.01.333

We have studied the evolution of the microstructure in solution-derived Ba0.5Sr0.5TiO3 (BST 50/50) thin films on alumina substrates prepared by multi-step rapid thermal annealing (RTA), i.e., by repeated deposition-pyrolysis-RTA steps. Upon annealing between 640 and 900 °C the thicknesses of the BST 50/50 films decrease from about 300 nm to about 240 nm, indicating progressive densification with an increased thermal budget. After RTA at 640 °C the films crystallize in a pure perovskite phase and consist of equiaxed grains that are about 10–20 nm across. When the temperature increases to 840 °C the microstructure coarsens only slightly. Only when annealing at temperatures ≥880 °C does the microstructure become predominantly columnar with a lateral grain size of about 90 nm. The evolution of the microstructure can be explained in the frame of the Microstructural Zone Model for solution-derived thin films (see Schuler et al. J. Sol-gel Sci. Techn., 2004), which relates the evolution of the film's microstructure with the ratio of the grain size and single-deposited-layer thickness, and provides guidance for designing the microstructure of BST films. In parallel with the observed changes in the microstructure, the kHz-range dielectric permittivity of the films increases by almost an order of magnitude, from around 180 to 1350. [Display omitted] •Solution-derived Ba0.5Sr0.5TiO3 thin films were prepared by multistep annealing.•The film microstructure, granular or columnar, is designed by annealing conditions.•The evolution of the microstructure is explained by the Microstructural Zone Model.•The dielectric permittivity spans from 180 to 1350 depending on the microstructure.