Spectroellipsometric studies of 0.9PbMg_1/3Nb_2/3O₃-0.1PbTiO₃thin films

0.9PbMg1/3Nb2/3O3-0.1PbTiO3(PMN-PT) films of different thickness, ranging from 75 to 450 nm, were prepared on La0.5Sr0.5MnO3(LSMO)-buffered LaAlO3(LAO) substrates by pulsed laser deposition (PLD). The structural properties of these films were characterized by X-ray diffraction. The θ-2θ scans indicated that all the films have a pure perovskite phase containing no impurity. The ω- and φ-scans confirmed that all the films possess a heteroepitaxial relation of PMN-PT(100) ∥ LSMO(100) ∥ LAO(100) structure. The surface morphology and cross section of the films were examined by scanning electron microscopy (SEM). Their dielectric constants and the leakage currents were measured by an impedance analyzer and a leakage digital electrometer, respectively. Furthermore, spectroellipsometry (SE) was used to characterize the depth profile, refractive index, and microstructural inhomogeneities, including voids, microroughness of surface, and the electrode/film interface of these films. Based on these studies, the correlation between the electrode/film interface and the electrical properties of the films was discussed. Our results show that the ratio of the electrode/film interface thickness to the film thickness increases as the film thickness decreases. The increase in this ratio results in deterioration of the leakage current and dielectric constant of the films.