Ferroelectric properties of direct-patternable la substituted Bi ₄Ti₃O₁₂ thin films formed by photochemical metal-organic deposition

The surface microstructure and ferroelectric properties of direct-patternable Bi_4-xLa_xTi₃O₁₂ (BLT) films prepared by photochemical metal-organic deposition as a function of La contents were characterized. The surface microstructure showed that La substitution (x = 0.75 and 1.00) to Bi₄Ti₃O₁₂ films was effective to induce an improved microstructure of the BLT films without the formation of surface holes. The measured remnant polarization values of BLT films with x = 0, 0.25, 0.50, 0.75, and 1.00 were 3.7, 7.1, 11.3, 16.0, and 8.1 μC/cm², respectively. After 10⁹ cycles, the remaining remnant polarizations of Bi_4-xLa_xTi ₃O₁₂ films with x = 0, 0.25, 0.50, 0.75, and 1.00 were 64.9, 69.5, 75.9, 94.8, and 95.0%, respectively. Considering the surface microstructure and ferroelectric properties of the BLT films, the BLT film with x = 0.75 showed the best microstructure and ferroelectric properties among all the BLT films. These results suggest the possible application of ferroelectric BLT film, relatively easily and without high cost process such as dry etching.