Microstructure analysis of epitaxial BaTiO₃ thin films on SrTiO₃-buffered Si: Strain and dislocation density quantification using HRXRD methods

Abstract

Barium titanate (BTO) is a promising perovskite-like material, exhibiting interesting functionalities, such as ferroelectricity, piezoelectricity, high dielectric constant, and electrooptic coefficients. All these properties are closely related to the orientation, density of linear defects and the stability of the tetragonal phase, which depends in turn on its fabrication conditions. High-vacuum Chemical Vapor Deposition (HVCVD) is a method allowing to deposit epitaxial BTO thin films on suitable substrates. In this study, we correlate the microstructure of BTO thin films to the Ba and Ti precursors flow parameters applied in the HVCVD process. In particular, strain, texture, and mosaicity of the crystalline blocks of BTO are investigated in both out-of-plane and in-plane orientation to assess the epitaxial relationships and the crystalline quality. The size of the BTO crystalline domains that scatter the X-ray radiation coherently is calculated using three methods. The mosaicity of the films has been correlated to the concentration of line defects. The value of the screw-type dislocations density has been derived and we discuss its close relationship with the coating deposition conditions.