Piezoelectric effect in epitaxial PbZr_(1-x)Ti_xO_3 thin films near morphotropic phase boundary region

摘要

The relationship between crystal structure and piezo-response was investigated in epitaxially grown PbZr_(1-x)Ti_x.O_3 (PZT) thin films on Pt(001)/MgO (001) with a thin PbTiO_3 interlayer. Insertion of the interlayer resulted in significant relaxation of the strain that could be developed in the course of deposition of the PZT films, consequently leading us to single out only the effect of composition. Composition of the morphotropic phase boundary (MPB), at which tetragonal and rhombohedral phases are mixed with the same volume fraction, was found to be approx 0.55 in Ti/(Zr + Ti) ratio in our films, which is close to the value for bulk polycrystalline PZT (approx 0.50). The piezoelectric response peaks were two times higher in the MPB regime than in the single phase regime due to structural instability caused by the coexistence of two phases. The results indicate that epitaxial PZT films having the MPB composition are advantageous over those of other compositions for nano-storage devices based on scanning force microscopy.