Crystallisation of Pb1-xCaTiO3 ferroelectric thin films as a function of the Ca2+ content

Lead calcium titanate (Pb1-xCaxTiO3) thin films with x from 0 to 0.50 were prepared by chemical solution deposition. Crystallinity of the films was studied as a function of calcium content and processing temperature. These studies were carried Out on films deposited onto oxidised (1 0 0) Si substrates by means of X-ray diffraction. The analysis seems to indicate that the grain size of the films decreases as Ca2+ content increases, which was confirmed from the scanning force microscopy images of the films. X-ray data reveal that kinetics of grain growth in films with Ca2+ contents over 40 at% is very slow. Increase of calcium also produces a decrease in tetragonality of the perovskite films. Besides, it was observed that reflections of the perovskite appear at higher temperature in the films with larger Ca2+ contents. Brillouin spectroscopy was used to follow the evolution of the elastic properties of the films with temperature. This study shows an elastic instability at temperatures between 475 degrees C and 500 degrees C that can be associated to complete film crystallisation. Dielectric and ferroelectric properties were measured on films deposited onto platinised silicon substrates and crystallised at 650 degrees C. The films with 50 at% of Ca2+ still have ferroelectric properties, showing diffuse ferro-paraelectric transitions and slim ferroelectric hysteresis loops. (c) 2005 Elsevier Ltd. All rights reserved.