Electrical and mechanical properties of ferroelectric thin films laser ablated from a Pb0.97Nd0.02(Zr0.55Ti0.45)O-3 target

Ferroelectric Nd-modified lead-zirconate-titanate (PZT) thin films were fabricated as capacitor structures with platinum electrodes using pulsed laser ablation deposition. Single-crystal MgO (100) and thermally oxidized Si (100) were used as substrates. The ablation processes were carried out at room temperature in a pressure of 4 X 10(-5) mbar in a vacuum chamber. A pulsed XeCl excimer laser with the wavelength of 308 nm was used for the ablation of both platinum and Pb0.97Nd0.02(Zr0.55Ti0.45)O-3 targets. For the PZT films with thicknesses between 300 and 600 nm, a laser-beam fluence of 1.0 J/cm(2) was used. Amorphous PZT films were postannealed at 675 and 650 degrees C in the cases of MgO and silicon substrates, respectively. The dielectric constant and the loss angle were measured at room temperature as a function of the film thickness. On the MgO substrate the dielectric constant of the films increased from 400 to 600 with the increasing film thickness, while in the films on the silicon substrate the dielectric constant was typically 140. The Curie temperature of the films was about 360 degrees C. The remanent polarization was about 18 mu C/cm(2) in the films deposited on MgO, but in the films on the silicon substrate the polarization values were much lower. The conductivity of the PZT thin films was studied as a function of temperature and electric field. Low-field resistivities of the order of 10(12) Omega cm were measured at room temperature. Macroscopic mechanical stresses in the PZT films were measured by the x-ray diffraction method. The films on the MgO substrate were in a compressive stress, while in the films on the silicon substrate a higher tensile stress was found. The dielectric constant was found to decrease and the coercive field to increase with the increasing mechanical stress. (C) 1997 American Institute of Physics.