Intrinsic crystalline structure of epitaxial Pb(Zr,Ti)O3 thin films -: art. no. 074101

We report on the intrinsic crystalline structure of epitaxial ferroelectric Pb(Zr,Ti)O-3 (PZT) films, which are fully relaxed from the stress of the substrate. The PZT films with the rhombohedral composition of Zr/Ti=68/32 were epitaxially grown on (001)Pt/(001)MgO substrates. Four-circle x-ray diffraction measurements revealed that the films showed not only perfect c-axis orientation, but also a tetragonal phase due to a clamping effect of the substrate. Successively, x-ray diffraction measurements using synchrotron radiation were carried out to examine the intrinsic structure of stress-free PZT films, which were powdered after substrate removal. The structure refinement by Rietveld analysis demonstrated that the films without substrates returned to a rhombohedral phase, however, 19% of the B site in the perovskite structure was occupied by Pb atoms. The phase-transition temperature from rhombohedral to cubic slightly decreased due to the anomalous structure of the stress-free PZT films. These results suggest that the deviation of the thin-film properties from the bulk ones is caused not only by in-plane epitaxial stress as an extrinsic factor, but also by the anomalous crystalline structure of the stress-free thin films. (C) 2005 American Institute of Physics.