Microstructure and ferroelectric properties of low-fatigue epitaxial, all (001)-orlented (Bi, La)_4Ti_3O_(12)/Pb(Zr_(0.4)Ti_(0.6)O_3/(Bi, La)_4Ti_3O_(12) trilayered thin films on (001) SrTiO_3 substrates

摘要

(Bi,La)_4Ti_3O_(12)(BLT)/Pb(Zr,Ti)O_3(PZT)/(Bi,La)4Ti_3O_(12) trilayered ferroelectric thin films were epitaxially grown by pulsed laser deposition onto (001) SrTiO_3 (STO) substrates with and without SrRuO_3 (SRO) bottom electrodes. From x-ray pole figures and electron-diffraction patterns, the epitaxial relationships between BLT, PZT, SRO, and STO were identified to be BLT(001)‖PZT(001)‖SRO(001)‖SrTiO_3(001); BLT[110]‖PZT[100]‖SRO[100]‖SrTiO_3[100]. Cross-sectional transmission electron microscopy investigations revealed that 90° ferroelectric domain boundaries lying on {110} planes are present in the PZT layer, with an average domain width of 20 nm and an average spacing of 120 nm. These long 90° ferroelectric domains, as a rule having nucleated at the bottom of the PZT layer, extend to the top of the latter. The thin films have sharp BLT/PZT interfaces and a very flat surface. The remanent polarization and coercive field were determined as 13.9 μC/cm~2 and 72.9 kV/cm, respectively, indicating that the epitaxial, all ((001)-oriented trilayered thin films have rather good ferroelectric properties, although single epitaxial (OOl)-oriented BLT films are usually not favored for application due to their very poor ferroelectric properties. The thin films showed a high fatigue resistance at least up to 10~(10) switching pulse cycles, confirming that such a trilayered structure effectively shows the fatigue-free behavior of BLT.