Polarized Raman scattering of highly [111]-oriented Pb(Zr,Ti)O3 thin films in the rhombohedral-phase field

Abstract

Highly [111]-oriented rhombohedral lead zirconate titanate [Pb(Zr1−xTix)O3;PZT] thin films were prepared on Pt(111)∕Ti∕SiO2∕Si substrates by suitably combining pulsed laser deposition with sol-gel coating. Two distinctive types of the backscattering geometry were employed for the polarized Raman scattering study: (i) normal backscattering in which the propagation direction of relevant phonons is parallel to the principal [111] polar axis of the rhombohedral 3m(C3v) point group for observing E(TO) phonons, and (ii) side-view backscattering in which the phonon-propagation direction is normal to the [111] direction for isolating A1(TO) phonons. Room-temperature Raman spectra of the [111]-oriented PZT60∕40 film (with Zr∕Ti=60∕40) having the high-temperature rhombohedral form were examined and compared with those of the [111]-oriented low-temperature rhombohedral PZT90∕10 film which is characterized by the tilting of oxygen octahedra about the principal [111] direction. Similarities and differences in the observed Raman spectra between these two distinctive films were examined in the light of the Raman selection rules for R3m and R3c space groups.