Effects of excess bismuth addition on the ferroelectric properties and memory characteristics of Bi3.25La0.75Ti3O12 thin films fabricated by sputtering

Bismuth lanthanum titanate (BLT) films with compositions of (1-x)Bi3.25La0.75Ti3O12 + xBi(2)O(3), where x = 0.28 - 0.36, were successfully deposited on Pt(111)/SiO2/Si(100) substrates by rf-magnetron sputtering using a powder target. All the BLT films were confirmed to have a single-phase bismuth-layer perovskite structure without the presence of a secondary phase. The x = 0.28 and 0.30 BLT films exhibited rounded grain morphologies with an average grain size of approximately 320 nm. On the other hand, BLT films with excess Bi2O3 of x >= 0.32 had significantly enhanced grain growth, exhibiting oval grain morphologies with an average grain size of approximately 500 nm x 200 nm. From the results for the J - E characteristics, the x = 0.30 BLT films showed the highest electrical insulation. The x = 0.30 BLT film also showed the best hysteresis loop shape with a remanent polarization of 2P(r) = 31 mu C/cm(2) and a coercive field of 2E(c) = 170 kV/cm. Measurements of the fatigue characteristics showed that all the samples exhibited nearly fatigue-free behavior that resisted degradation even after 1 x 10(10) cycles.