Processing- and composition-dependent characteristics of chemical solution deposited Bi_(4-x)La_xTi_3O_(12) thin films

摘要

Thin films of lanthanum substituted bismuth titanate, Bi_(4-x)La_xTi_3O_(12) (BLTx), were prepared by chemical solution deposition. Crystallized BLTx films were obtained by rapid thermal annealing at a temperature as low as 650 deg C. Structural and electrical characteristics of crystalline BLTx films were studied as functions of La composition. Structure characterization was conducted by x-ray diffraction and Raman spectroscopy. The lowest lattice vibration mode around 116 cm~(-1) showed softening with increasing lanthanum composition. Surface morphology of BLTx films were recorded by scanning electron microscopy. BLTx films have saturated hysteresis loops with remnant polarization of 9.7, 12.3, and 4.5 #mu#C/cm~2, respectively, for x = 0.50, 0.75, and 1.00 films. BLT0.75 films showed fatigue-free behavior over 250 kV/cm, 50 kHz cycling, which could be compared with that of SrBi_2Ta_2O_9 thin films. Fatigue resistance decrease at lower cycling field. The field dependence of fatigue property was discussed briefly in terms of competition between domain pinning and field-assisted unpinning.