Crystallographic orientations and electrical properties of Bi3.47La0.85Ti3O12 thin films on Pt/Ti/SiO2/Si and Pt/SiO2/Si substrates

We report on the crystallization and electrical properties of Bi3.47La0.85Ti3O12 (BLT) thin films for possible ferroelectric nonvolatile memory applications. The film properties were found to be strongly dependent on process conditions especially on the intermediate heat treatment conditions. The crystallographic orientation of the films showed sharp changes at the intermediate rapid thermal annealing (RTA) temperature of 450degreesC. Below 450degreesC, BLT thin films have <117> orientation while they have preffered c-axis orientation above 450degreesC. We found that RTA conditions of the first coating layer play a major role in determining the entire crystallographic orientation of the films. The films also showed of ferroelectric hysterisis behavior strongly dependent on RTA treatment. In fact, the remanent polarization of Bi3.465La0.85Ti3O12 thin films having <001> preferred crystallographic orientation showed much smaller value compared to those having <117> orientation. The BLT films also exhibited good fatigue characteristics under bipolar stress up to 10(11) cycles regardless of their intermediate thermal treatments.