Retention characteristics of (Bi,La)₄Ti₃O ₁₂ films on Si(100) substrates using LaAlO₃ buffer layers

We demonstrate the ferroelectric behavior of (Bi,La)₄Ti ₃O₁₂ (BLT) films deposited on Si(100) substrates by using LaAlO₃ buffer layers. LaAlO₃ films were prepared by molecular beam deposition method. Then, they were subjected to ex situ dry N₂ annealing in a rapid thermal annealing furnace. From the capacitance-voltage measurement, the dielectric constant of LaAlO₃ was estimated to be 20 to 26. On these structures, BLT films were deposited by sol-gel method and they were characterized by X-ray diffraction analysis. It was found from capacitance-voltage measurements that the characteristics showed a hysteresis loop and the memory window was about 0.5 V for the voltage sweep of ±9 V. It was also found from the retention measurement that the higher and lower capacitance values in the hysterisis loop could be distinguished at least for 3 days. It is concluded from these results that the BLT/LaAlO ₃/Si(100) structure is one of the most promising structures for realizing MFISFETs (metal-ferroelectric-insulator-semiconductor field effect transistors).