X-ray diffraction study on the grain-size-dependences of orientation and 90 °-domain structure in oriented PbTiO3 thin films on (111) Pt

Abstract

Both (100) and (001) oriented PbTiO3 thin films were prepared on (111) Pt substrates using a sol-gel process. It is indicated that very-fine-grained (< 100 nm) thin films are difficult to align with the substrates. More importantly, the X-ray diffraction (XRD) evidences of the absence of 90 °-domains are found in oriented films with fine grains. In the XRD pattern of coarse-grained (≈ 210 nm) films, the intensity ratio of peaks (100) and (001) is close to that for powder PbTiO3. As the average grain size decreases to 130 nm with annealing temperature, the intensity of the peak (100) increases drastically while that of (001) decreases rapidly. The sudden changes in the relative intensities of the two peaks suggest that at grain size below a critical size between 130 and 210 nm most of the grains in the films no longer show 90 °-domains, which is in good agreement with our TEM investigations for randomly oriented PbTiO3 thin films. These interesting results have not been previously reported.