Quantitative texture analysis applied to the study of preferential orientations in ferroelectric thin films

Abstract

The occurrence of preferred crystallographic orientations, or texture, is a determinant factor of the behaviour of polar materials, like ferroelectric thin films. This is the reason why numerous works have been focused in the preparation of highly oriented films for pyroelectric sensors and electromechanical applications. Traditionally, preferred orientations were determined by the analysis of the main reflections obtained by X-ray diffraction, which only in some cases are characteristic of the texture of the material. Regardless of the interest of this subject, the quantitative texture analysis of ferroelectric thin films has not been systematically applied. This consists in the measurement of pole figures with a goniometer, and the determination of the orientation distribution function. In this work we summarise briefly the principles of the quantitative texture analysis and we demonstrate its application to the study of different ferroelectric thin films: La and Ca modified lead titanate (PTL and PTC) and lead zirconate titanate (PZT). This method allows the study of the characteristics of the type of texture and the identification of the different components that contribute to the final texture of the material. An indicative value of the texture strength is also obtained for both the ferroelectric film and the substrate layers. This information allows us the study of the process that leads to the orientation in thin films, and to obtain correlations between texture and physical properties.