Characteristics of some (MOD) thin film layer type compounds in the bismuth titanate-lead titanate system

Layer type Aurivillius compounds of complex ferroelectric bismuth oxides have become important as thin films for nonvolatile, random-access memories(DRAMS). This paper reports the investigation of the formation of these compounds and their electrical properties, in the bismuth titanate-lead titanate system. Films were formed using the metallo-organic decomposition (MOD) spin-on solution process. These solutions were spun onto a platinized Si substrate and then fired at 700°C to form 1 μm thick films of bismuth titanate and lead titanate. The films were analyzed using microprobe and x-ray diffraction analyses. Next, the solutions were blended to give compounds from m = 4 to m = 7; where m is defined as the potential number of perovskite-like units between (Bi2O2)+2 layers. The blended solutions were processed exactly like the bismuth titanate and lead titanate solutions. X-ray diffraction analysis was used to determine if Aurivillius layer compounds were formed. Ferroelectric hysteresis loops were correlated with the results obtained from the x-ray diffraction studies.