Crystallographic characterization of tetragonal (Pb,La)TiO3 epitaxial thin films grown by pulsed laser deposition

Abstract

Crystallographic properties such as lattice constants, degree of c-axis orientation, and c/a ratio of tetragonal Pb1−xLaxTiO3 (PLT, x=0–0.28) epitaxial thin films grown by pulsed laser deposition on single-crystal substrates such as MgO(001) and SrTiO3(001) were evaluated. General x-ray-diffraction techniques—θ-2θ scan and Φ scan—were used to confirm the epitaxial relations between films and substrates. The epitaxial relations were PLT(001) or (100)//substrate (001) and PLT[100] or [001]//substrate[100]. Then, using the {303} asymmetric rocking curve technique, more quantitative crystallographic informations of PLT films could be obtained. The c/a ratio and lattice constant along the a axis of c-axis-oriented PLT tetragonal unit cell were calculated from the peak location of {303} rocking curve, which is slightly different from that of the powder or bulk PLT. The existence of a-axis-oriented domains was also verified in PLT films grown on SrTiO3 substrate by {303} rocking curve. The origin of the observed ferroelectric domain structures is discussed based on transformation and thermal strains involved in the film preparation.