Study on the orientation degree of Pb 1 − xLa xTiO 3 thin films by the rocking curve technique and its morphological aspects

J.H.G Rangel,M.I.B Bernardi,C.A Paskocimas,E Longo,J.A Varela

doi:10.1016/j.surfcoat.2006.11.039

Abstract

Thin films of perovskite-type materials such as PbTiO 3, BaTiO 3, (Pb,La)TiO 3, (Pb, La)(Zr,Ti)O 3, KNbO 3, and Pb(Mg,Nb)O 3 have been attracting great interest for applications like non-volatile memories, ultrasonic sensors and optical devices. Thin film should be epitaxially grown or at least highly textured since the properties of this anisotropic material depend on the crystallographic orientation. For optical devices, in particular, an epitaxial thin film without defects are essential to reduce optical propagation losses. Pb 1 − x La x TiO 3 (PLT) where x = 0, 13 and 27% thin films were prepared by a chemical method (polymeric precursors method), and deposited by the spin coating technique onto substrates of SrTiO 3 (STO) and LaAlO 3 (LAO). The films were then heat treated at 500 °C in a controlled atmosphere of O 2. The orientation degree of the thin films was obtained from rocking curve technique, by means of X-ray diffraction analysis. A microstructural study revealed that the films were crack-free, homogeneous and have low roughness.

Highlights

Lead titanate (PT) is a well known ferroelectric ceramic with interesting dielectric, pyroelectric and piezoelectric properties [1]
The 0-Pb1 − xLaxTiO3 (PLT), 13-PLT and 27-PLT thin films, with four layers, deposited onto substrates of STO, and PLT films with the same chemical composition with six layers deposited onto LAO substrates were analyzed by X-ray diffraction, as shown in Figs. 2 and 3, respectively
In the diffraction patterns of the STO-deposited films, the peaks indicated that a tetragonal phase formed for the 0-PLT films, while peaks corresponding to a cubic phase were present for the 13- and 27-PLT films

Summary

Introduction

Lead titanate (PT) is a well known ferroelectric ceramic with interesting dielectric, pyroelectric and piezoelectric properties [1]. The sol–gel process is well suited to the preparation of powders and thin film of PT [3] This process involves the preparation of polymerisable solutions, which is diluted and. For many applications, such as waveguides, polycrystalline thin films with random crystallographic orientations are not appropriate and, high degree of orientation or monocrystalline films are required. In a polycrystalline system this phenomenon causes light dispersion, increasing the optical attenuation of the film Besides this intrinsic effect, there are other factors of major importance such as point defects and crystallographic imperfections [4,5,6,7]. The orientation degrees of these films were determined by means of the full width at half-maximum (FWHM) of the rocking curves

Experimental

X-ray diffraction

Rocking curve

Conclusion