A combination of piezoresponse force microscopy and x-ray diffraction sin2Ψ stress measurement have been used to investigate domain evolutions in (111)-oriented Pb(Zr0.55Ti0.45)O3 (PZT) and (115)-oriented SrBi2Ta2O9 (SBT) thin films with the repeated switching cycles (fatigue process). In the PZT film, it has been found that 90° a-c domain walls form at the beginning of fatigue process and increase in amount with accumulation of switching cycles, accompanied by increase of stress. However, domain pattern and stress in the SBT film seem to be unchanged as the fatigue process is going on. The increase in stress with the repeated switching cycles in the PZT film can be attributed to the lattice distortion caused by polarization rotation. On the contrary, polarization switching in SBT involves little lattice distortion and lets it in a nearly stress-free status during the fatigue process. The difference in domain evolution during the fatigue process suggests the important role of stress in fatigue behaviors of PZT and SBT films.

No abstract

No abstract

Nanoscale switching of the lamellar 90 • domains (a-a domains) of PbTiO 3 grains in the surface of sol-gel-derived PbTiO 3 /Pb(Zr 0.58 Ti 0.42 )O 3 /PbTiO 3 thin films is studied by three-dimensional piezoresponse force microscopy. It is demonstrated that the lamellar domain pattern in the PbTiO 3 grains can be rotated 90 • in the plane of film by the electric field at the tip. It is found that the rotation of lamellar domain pattern involves transverse growth of the existing embedded a-a domain nucleus, whose domain walls are perpendicular to the surrounding ones. During the transverse growth, the existing 90 • domains extend along length direction and penetrate into neighboring domain walls, while formation of new 90 • domain walls was mediated by the nanoscale 45 • tilted spike domains.

Ferroelectric SrBi 1.4 La 0.6 Ta 2 O 9 (SBLT) thin films were grown onto Pt/Ti/SiO 2 /Si substrates by pulsed-laser deposition. With the aid of X-ray diffractometry, piezoresponse scanning probe microscopy, and ferroelectric-property measurements, a correlation between microstructure, as well as domain structure and ferroelectric properties, was established. Excluding the effect of preferential orientation on ferroelectric properties, the increase in remanent polarization was attributed to distortion of the perovskite-like sublattice and atom displacement. Despite the coinstantaneous observation of a 901 domain and slight fatigue behavior in the SBLT films, the 901 domain-wall clamping did not seem to account for the fatigue in the SBLT films. Instead, strain-stress aggravation of the SBLT sublattice, due to the substitution of La 31 into Bi 31 sites, decreased the self-regulated flexibility of the (Bi 2 O 2 ) 21 layers and caused fatigue in the SBLT.