Composition dependence of the ferroelectric properties of lanthanum-modified bismuth titanate thin films grown by using pulsed-laser deposition

Lanthanum-modified bismuth titanate, Bi4-xLaxTi3O12 (BLT), thin films with a La concentration of 0.25 less than or equal to x less than or equal to 1. 00 were grown on Pt/Ti/SiO2/Si substrates by using pulsed-laser deposition. The BLT films showed well-saturated polarization-electric field curves who se remnant polarizations were 16.1 mu C/cm(2), 27.8 mu C/cm(2), 19.6 mu C/c m(2), and 2.7 mu C/cm(2), respectively, for x=0.25, 0.50, 0.75, and 1.00. T he fatigue characteristics became better with increasing x up to 0.75. The Au/BLT/Pt capacitor with a La concentration of 0.50 showed an interesting d ependence of the remanent polarization on the number of repetitive read/wri te cycles. On the other hand, the capacitor with a La concentration of 0.75 showed fatigue-free characteristics.