Microstructure and electric properties of lead lanthanum titanate thin film under transverse electric fields

Abstract

Polycrystalline lead lanthanum titanate thin film having perovskite structure was fabricated by metalorganic deposition (MOD) on a ZrO₂/SiO₂/Si substrate at 600°C for 1 h in O₂ atmosphere. Columnar structured ZrO₂ buffer layer was also prepared by a MOD process under the same condition. Electrical measurements were conducted on interdigitated electrodes. The crystalline structure and growth behavior of the films have been studied by x-ray diffraction and scanning electron microscopy. It is observed that dielectric response of the film is effected by the cable length used in the measurement and by the values of the ac voltage. Long cable gives rise to an additional resonance peak at high frequency caused by the stray inductance of the contacts and cables. The capacitance and loss tangent over low frequency range shows significant variations due to the trapped charges and space charges in the film. These variations are very dependent on the values of the ac voltage and the length of cable. Meanwhile, the trapped charges and space charges lead to abnormal P-E loops, in which the measured remanent polarization and coercive field increase with increasing frequency.