Improvement of the fatigue and the ferroelectric properties of PZT films through a LSCO seed layer

The ability to optimizate the preparation of Lead Zirconate Titanate (PZT) films on platinized Si substrate by pulsed laser deposition was demonstrated. The effect ofthe modification ofthe interface film/electrode through the use of a (La,Sr)CoO3 (LSCO) seed layer on the remnant polarization, fatigue endurance and stress in PZT films was studied. An improvement on the ferroelectric properties was found with the using of the LSCO layer. A remnant polarization (Pr) of 19.8 C/cm2 and 4.4 C/cm2 for films with and without the LSCO layer were found. In the same way the polarization fatigue decreases significantly after deposition of the LSCO layer between the film and substrate. Atomic force microscopy (AFM) images revealed a different growth process in the films. Current–voltage (I–V) measurements showed that the use of LSCO seed layer improves the leakage current and, on the other hand the conduction mechanisms in the film without LSCO, after the fatigue test, was found to be changed from Schottky to Poole–Frenkel. The trap activation energy (about 0.14 eV) determined from Poole–Frenkel mode agrees well with the energy level of oxygen vacancies. The films stresses were estimated by XRD in order to explain the improvement on the structure and consequentially ferroelectric properties of the films. The model proposed by Dawber and Scott was found to be in agreement with our experimental data, which seems to predict that the oxygen vacancies play an important role on fatigue.This work was partially supported by the Portuguese Foundation for Science and Technology (FCT) through the Pluriannual Project of Centre of Physics of University of Minho. S.A.S.R. thanks FCT for the financial support (grant SFRH/BD/30531/2006). J.P.B.S. thanks FCT for the financial support (grant SFRH/BD/44861/2008). J.M.S. thanks FCT for the financial support (grant SFRH/BPD/64850/2009)

Multilayers of Ge nanocrystals embedded in Al2O3 matrix: Structural and electrical studies

In this paper, Ge/Al2O3 multilayer systems were grown by pulsed laser ablation. The grown samples were annealed at 900 °C to promote the formation of Ge nanocrystals. Rutherford backscattering spectroscopy and transmission electron microscopy confirmed the presence of a multilayer system. Grazing incidence small angles X-ray scattering technique demonstrates the formation of Ge nanoclusters formed between alumina layers. Room temperature I–V measurements showed weak carrier trapping in the system. This was explained by the leakage caused by Ge diffusion through the multilayer