Effect of pretreatments on the ferroelectricity of (Pb,Ca)TiO3 thin films

Calcium-substituted PbTiO3 thin films prepared by a sol-gel method, deposited by spin-coating onto Pt/TiO2/SiO2/(100)Si substrates and crystallized by a rapid heating at 650 degrees C for 12 min, have been subjected to conditioning treatments prior to their polarization. An electrical treatment, a second annealing of the crystalline film at 650 degrees C with a slow heating rate of 10 degrees C/min and a rapid heating at 500 degrees C of the films with the top electrodes deposited, have been tested and their effect on the further polarized films studied. An these pretreatments improve the ferroelectric characteristics of the films. But the annealing at 650 degrees C leads to the optimum ferroelectric response of the films prepared with a 10 mol% excess of lead oxide. This treatment produces the redistribution of the charged defects generated during the preparation of the films, mainly vacancies and holes. Films with remanent polarizations of about delta P similar to 40 mu C/cm(2) that remain over 2 mu C/cm(2) after 10(5) s and after 10(7) cycles are obtained. (C) 1998 Elsevier Science Ltd. Ail rights reserved.