In-situ observation of ultrafast 90° domain switching under application of an electric field in (100)/(001)-oriented tetragonal epitaxial Pb(Zr0.4Ti0.6)O3 thin films

Abstract

Ferroelastic domain switching significantly affects piezoelectric properties in ferroelectric materials. The ferroelastic domain switching and the lattice deformation of both a-domains and c-domains under an applied electric field were investigated using in-situ synchrotron X-ray diffraction in conjunction with a high-speed pulse generator set up for epitaxial (100)/(001)-oriented tetragonal Pb(Zr_0.4Ti_0.6)O₃ (PZT) films grown on (100) _c SrRuO₃//(100)KTaO₃ substrates. The 004 peak (c-domain) position shifts to a lower 2θ angle, which demonstrates the elongation of the c-axis lattice parameter of the c-domain under an applied electric field. In contrast, the 400 peak (a-domain) shifts in the opposite direction (higher angle), thus indicating a decrease in the a-axis lattice parameter of the a-domain. 90° domain switching from (100) to (001) orientations (from a-domain to c-domain) was observed by a change in the intensities of the 400 and 004 diffraction peaks by applying a high-speed pulsed electric field 200 ns in width. This change also accompanied a tilt in the angles of each domain from the substrate surface normal direction. This behaviour proved that the 90° domain switched within 40 ns under a high-speed pulsed electric field. Direct observation of such high-speed switching opens the way to design piezo-MEMS devices for high-frequency operation.

Figure 1

HRXRD 2θ-ω mappings near (a) PZT 400 and (b) PZT 004 for (100)/(001)-oriented epitaxial tetragonal Pb(Zr_0.4Ti_0.6)O₃ films. (c) Schematic representation of the domain structure.

Figure 2

HRXRD 2θ scans of (a) PZT 004 [scan II in Fig. 1(b)] and (b) PZT 400 [scan I in Fig. 1(a)] measured under a 200-ns pulsed electric field with amplitudes of 0 kV/cm (open squares) and 170 kV/cm (filled circles) for the same Pb(Zr_0.4Ti_0.6)O₃ films shown in Fig. 1.

Figure 3

Rocking curves (ω scans) of (a) 004 PZT under 0 kV/cm (open squares) and 170 kV/cm (filled circles) in scan V in Fig. 1(b). (b,c) Rocking curve of 400 PZT under 0 kV/cm (open squares) and 170 kV/cm (filled circles) of image in (b) scan III and (c) scan IV in Fig. 1(a), respectively.

Figure 4

(a) Capacitance and (e) calculated differential capacitance by time as a function of time during application of a 200-ns pulsed electric field with a magnitude of 170 kV/cm. The solid line in panel (a) indicates applied pulse voltage measured by reference capacitor. (b) Strain, (c) tilting angle, (d) intensity, and (f)V _c of PZT 400 (circles) and PZT 004 (squares) peaks as a function of time during application of a 200-ns pulsed electric field with a magnitude of 170 kV/cm. Iintensities are integrated one obtained by peak fitting. Open circles and squares are calculated by the 004 diffraction peak from the c-domain and the 400 diffraction peak from the a-domain, respectively. Total strain including extrinsic contribution (open diamond) was also plotted in panel (b).