Preferential Creation of Polar Translational Boundaries by Interface Engineering in Antiferroelectric PbZrO₃ Thin Films

Abstract

the paraelectric to AFE phase transition, cell quadrupling in PbZrO 3 results in the appearance of TBs. These boundaries are characterized by translation vectors R = [ a / n 1 , b / n 2 , c / n 3 ], 1/ n i ( i = 1, 2, 3), which are fractions of the unit-cell translation vectors. In this work, we report on the relation between formation of polar TBs and the interfacial strain in the system of PbZrO 3 thin fi lms grown on SrTiO 3 substrates. In combination with geometric phase analysis (GPA), [ 28 ] high-angle annulardark-fi eld (HAADF) imaging and Stripe scanning transmission electron microscopy (STEM) techniques based on aberrationcorrected STEM allowed us to determine the structural arrangement and strain distribution near the interfaces.Epitaxial PbZrO 3 thin fi lms were grown on (100) SrTiO 3 substrate and on BaZrO 3 -buffered (100) SrTiO 3 substrate (see the Experimental Section for details). As the lattice parameters of PbZrO 3 are larger than that of SrTiO 3 , the BaZrO 3 buffer layer is used to modulate the misfi t between the PbZrO 3 fi lm and the SrTiO 3 substrate. Figure 1 a shows a plan-view bright-fi eld TEM image of a PbZrO 3 fi lm on BaZrO 3 buffered (100) SrTiO 3 substrate. The dark dot contrast in the image originates from threading dislocations in the fi lm arising from the threading segments associated with the misfi t dislocations due to the lattice mismatch. The HAADF-STEM image of the cross-sectional sample (Figure 1 b) shows morphology of the fi lm system with ≈35 nm thick PbZrO 3 fi lm. In the medium-magnifi ed HAADF image, Figure 1 c, one can clearly see that the PbZrO 3 fi lm is epitaxially grown on the BaZrO 3 buffer layer. Due to antiparallel displacements of Pb atoms and antiphase rotation of the octahedra, [ 29,30 ] the AFE structure characterized by the (010) and (021) refl ections, which are the superstructure refl ections of q Σ = 1/4(110) p and q R = 1/2(111) p with respect to the pseudocubic structure, [ 31 ] can clearly be identifi ed from the fast Fourier transformation (FFT) image illustrated in Figure 1 d. Considering that the image intensities are atomic-number dependent and roughly proportional to Z 2 , [ 32 ] the TBs residing inside the AFE domain areas can be directly observed based on the antiparallel displacements of the heavy Pb atoms along the orthorhombic [100] direction. A typical APB on the atomic scale, type R III-1 = 1/4 [02 n ] ( n = 0 or 2) is shown in Figure 1 e.Based on atomic scale investigation and analysis of GPA on the HAADF images, all types of TBs in the AFE PbZrO 3 thin fi lms were studied and the results are given in Table 1 . Figure 2 a shows the morphology of two types of TBs, the R III-1 and R I-1 = 1/4 [21 n ] type boundaries, in the 35 nm thick fi lm. The characteristic displacements of the Pb atoms are displayed as a function of the distance away from the boundary centers in Figure 2 b. Based on the average displacements (33.1 pm) of the Pb atoms away from their ideal positions, the spontaneous polarization is estimated as P S = 16 and 17 µC cm ...

An Unconventional Transient Phase with Cycloidal Order of Polarization in Energy‐Storage Antiferroelectric PbZrO3

“…Specifically, it is found that tails of the 2D polarization vectors, composed of the fitted sinusoidal profiles, can be nicely approximated by a curtate cycloid, which has a periodicity of 4 b O along the y direction (Figure c; Figure S5, Supporting Information). When structural defects appear, e.g., the translational boundaries, the commensurate relation of polarization with lattice will be broken in periodicity.…”

“…Information). When structural defects appear, e.g., the translational boundaries, [35,36] the commensurate relation of polarization with lattice will be broken in periodicity.…”

Antiferroelectrics: History, fundamentals, crystal chemistry, crystal structures, size effects, and applications

“…Also, compositional and mechanical tuning seem to favor the formation of certain types of antiphase boundaries. 213…”

“…It should be noted that antiphase boundaries with different translational vectors exhibit different polar states, 212 Figure 27B just illustrates one of the simplest cases. Also, compositional and mechanical tuning seem to favor the formation of certain types of antiphase boundaries 213 …”

In Situ Observation of Point‐Defect‐Induced Unit‐Cell‐Wise Energy Storage Pathway in Antiferroelectric PbZrO3

“…[ 23–25 ] As a factor of reducing the U e , the inescapable P r , irrelevant to antiparallel cation shifts with either complete or partial offset, motivates us to find out its relationship with the ubiquitous structural defects, for example, point and planar defects. [ 26–28 ]…”