Relaxation of induced polar state in relaxor PbMg1∕3Nb2∕3O3 thin films studied by piezoresponse force microscopy

Abstract

Polarization state in epitaxial thin films of relaxor ferroelectric PbMg1∕3Nb2∕3O3 (PMN) was experimentally studied at the nanoscale using a piezoresponse force microscopy (PFM). In the absence of a dc bias applied to the PFM tip, no piezoelectric activity could be found on most of the surface of the film. Under a moderate voltage (>1.5–2V), a polar state with a nonzero piezoresponse could be induced. Longer poling resulted in a significant reduction of the initial piezoresponse. After removing the bias field, a long-term relaxation of the piezoelectric signal obeying a Kohlrausch-Williams-Watt dependence was observed.

Ferroelectric domain structure of anisotropically strained NaNbO3 epitaxial thin films

“…In relaxors, weakly interacting polar nanometer-size regions are formed, leading to low polarization contrast, uniformly distributed directions of the dipole moments and diffuse domain walls. 44 Similar results have been described for compressively strained BiFeO 3 thin films on LaAlO 3 substrates 47 and Bi 1/2 Na 1/2 TiO 3 -BaTiO 3 ceramics, 43 which exhibit likewise relaxor properties. Ongoing advanced experiments regarding the domain switching after DC poling and relaxation as well as temperature dependent PFM have also suggested relaxor behavior.…”

“…Since amplitude and phase images of the LPFM and VPFM measurements exhibit no contrasts and nearly no domain-related features are discernible, we do not show the PFM measurements on 10 nm thin films here. The absence of any contrasts in PFM measurements also has been observed in literature for Bi 1/2 Na 1/2 TiO 3 -BaTiO 3 derived ceramics 43 and PbMg 1/3 Nb 2/3 O 3 thin films 44 and was attributed to relaxor properties of the samples. It should be noted that the occurrence of an in-plane polar component cannot be explained if the in-plane anisotropy of lattice strain is neglected.…”

Mapping bias-induced phase stability and random fields in relaxor ferroelectrics

“…In classical ferroelectrics, the material evolution can be well described as the sequential intrinsic domain nucleation and subsequent domain growth by wall motion. 22 A number of observations suggest that the polarization reorientation mechanism in relaxors is drastically different, and proceeds through a gradual evolution and decay of bias-induced states 16,23 similarly to the macroscopic case. 24 Comparison with relaxation studies suggests that the loops in PMN-10%PT are related to a large bias-induced polarization with a relaxation time of ϳ10 s, 16 i.e., much longer than the dc bias cycling in the SS-PFM experiments.…”

Local piezoresponse and polarization switching in nucleobase thymine microcrystals

“…These results are similar to those obtained in ferroelectric relaxors, where the bias-induced reversible ferroelectric-relaxor phase transition resulted in a similar response. 55 This again hints to the significant disorder of the crystals, especially between the layers.…”