THE PROPERTIES OF LEAD TITANATE THIN-FILMS PRODUCED BY CHEMICAL-VAPOR-DEPOSITION

This project focused on advancing the knowledge of chemical vapour dep osition (CVD) of lead titanate (PbTiO3) thin films for future work on lead zirconate titanate or PZT (PbZrxTi1-xO3) through an understanding of the structural, chemical, and electrical properties of the materia l. A low-pressure, low-temperature process for PbTiO3 was developed. T he major factors in controlling the film composition and thickness uni formity were identified as substrate temperature and the partial press ures of the reactive gases. The formation sequence for CVD PbTiO3 film s involved individual oxides of Ti and Pb, rather than pyrochlore-type phases. A Pb-rich composition ensured the formation of perovskite, ho wever, it resulted in the formation of a thin PbOx surface layer. Remo val of this layer by etching gave improved electrical properties. Capa citance measurements typically varied less than 1% over the frequency range and gave epsilon' values from 60 to 155. At 1 kHz, tan partial d erivative was similar to 0.01 and the resistivity was similar to 10(11 ) Ohm cm. Transmission electron microscopy examination of as-deposited films of PbTiO3 revealed no macrodomains existed. After post-depositi on rapid thermal annealing (RTA), twinned structures, apparently actin g as domains, were found in similar to 0.1 mu m diameter grains. The m ultilayered bottom electrode of Pt and Ti used in this study was found to react at temperatures less than or equal to 515 degrees C. At high er RTA temperatures (698 degrees C), the Ti layer was completely consu med, however the top surface of the Pt layer remained unaffected.