Polarization pattern at the atomic scale in ferroelectric BaTiO3 under different boundary conditions by HRSTEM
2Centre Raimond Castaing, CNRS and Université de Toulouse, Toulouse, France
3Functional Oxides for Energy-Efficient Information Technology, Helmholtz Zentrum Berlin für Materialien und Energie, Berlin, Germany
4Physical Chemistry, Freie Universität Berlin, Berlin, Germany
5Instituto de Nanociencia y Materiales de Aragón, Universidad de Zaragoza, Zaragoza, Spain
6Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, Zaragoza, Spain
Ferroelectrics are attractive materials for applications such as sensors and communication devices, among others1. For this, it is necessary to combine the ferroelectric material with a semiconductor substrate and often use a buffer layer (for example, SrTiO3) at the interface to control the epitaxial strain. The imposed boundary conditions determine the polarization pattern of the ferroelectric layer, and exotic polar textures may arise when dimensions are decreased to a few nanometers2,3. In this work, the polarization distribution of BaTiO3 was studied in bulk, thin film, and nanopillar forms.
BaTiO3 thin films were grown by molecular beam epitaxy on SrTiO3-buffered (001) Si substrate1, and neon ion beam milling (NIM) was used for nanopillar fabrication in films and BaTiO3 single crystals. Surface protection was applied before NIM to avoid surface amorphization. High-resolution scanning transmission electron microscopy (HRSTEM) was used to image Ti and Ba atomic columns along the [010] direction. Ti polar displacement vector direction and amplitude with respect to the barycenter of each Ba unit cell were mapped over the images by 1) Atomap4, a real space method based on the 2D-Gaussian fitting of the atomic positions, and 2) AbStrain5, a reciprocal space method newly developed at CEMES.
It was possible to identify the presence of nanometric domains in the BaTiO3 thin films with uniform polarization and exotic polar patterns, while larger domains were observed in the BaTiO3 single crystal. The information gained from Atomap and Abstrain will be discussed, and the difference in polarization patterns between thin films and nanopillars will be presented.
References:
1. L. Mazet, et al. Sci. Technol. Adv. Mater. 16 (2015)
2. S. Das et al. APL Mater. 8 (2020)
3. A. Fernandez et al. Adv. Mater. 34 (2022)
4. M. Nord, et al. Adv. Struct. Chem. Imag. 3 (2017)
5. N. Cherkashin, GADEST-19, (2022) and this conference
Powered by Eventact EMS