PREPARATION AND CHARACTERIZATION OF LEAD ZIRCON ATE TITANATE THIN FILMS BY SOL-GEL PROCESSES

Ferroelectrics have recently undergone a renewed interest due to the wide range of properties which can be conveniently exploited in the form of thin films. As pyroelectrics and piezoelectrics they can be integrated into silicon technology and their ferroelectricity can be used at voltages compatible with integrated circuits. Different techniques are being employed to make these flims, such as sputtering, laser ablation, however sol-gel methods are a useful and inexpensive route for making films of good quality over large areas. In this work lead titanate (PT) and lead zirconate titanate (PZT) thin films were made from sols spun onto (1 (0) silicon and sputtered platinum substrates. Two types of heat treatment were used to form the ceramic; a normal heat treatment where the sample is heated and cooled within the furnace and a rapid thermal process where the sample, by moving it in and out of 62 the furnace, is subjected to heating rates of about 100 K/min. The latter method gives specular, crack free films but the stresses induced by the rapid temperature changes led to defects at the substrate interface. Profilometry and electron microscopy confmn the homogeneity of the thickness. In addition the crystallization mechanism was studied using DTA, TGA, X-ray diffraction and infra-red spectroscopy. The results show that sol-gel techniques crystallize ceramics at low temperatures, compatible with semiconductor technology but the mechanisms of crystallization of bulk and thin ftlm gels differ. C-V measurements and dielectric hysteresis curves were recorded as a function of heat treatment and also compared for the two different heating methods