Crystallographic Orientations and Electrical Properties of Bi3.47La0.85Ti3O12 Thin Films on Pt/Ti/SiO2/Si and Pt/SiO2/Si Substrates

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We report on the crystallization and electrical properties of Bi3.47La0.85Ti3O12 (BLT) thin films for possible ferroelectric non-volatile 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 450°C. Below 450°C, BLT thin films have $\langle 117 \rangle$ orientation while they have preffered $c$-axis orientation above 450°C. 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 $\langle 001\rangle$ preferred crystallographic orientation showed much smaller value compared to those having $\langle 117\rangle$ orientation. The BLT films also exhibited good fatigue characteristics under bipolar stress up to $10^{11}$ cycles regardless of their intermediate thermal treatments.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2003-04-15