Nanosecond Domain Wall Dynamics in Ferroelectric $\mathrm{Pb}(\mathrm{Zr},\mathrm{Ti}){\mathrm{O}}_3$ Thin Films

Domain wall motion during polarization switching in ferroelectric thin films is fundamentally important and poses challenges for both experiments and modeling. We have visualized the switching of a $\mathrm{Pb}(\mathrm{Zr},\mathrm{Ti}){\mathrm{O}}_3$ capacitor using time-resolved x-ray microdiffraction. The structural signatures of switching include a reversal in the sign of the piezoelectric coefficient and a change in the intensity of x-ray reflections. The propagation of polarization domain walls is highly reproducible from cycle to cycle of the electric field. Domain wall velocities of $40\mathrm{m}{\mathrm{s}}^{-1}$ are consistent with the results of other methods, but are far less than saturation values expected at high electric fields.

Figure 1

Time-resolved x-ray microdiffraction measurement of the $2\theta$ angle of the PZT (002) Bragg reflection as a function of the delay time after the onset of an 8 V electrical pulse. The effective time resolution of the measurement, corresponding to the 90% to 10% transition time, is 620 ps.

Figure 2

(a) The intensity of the PZT (002) Bragg reflection as a function of $\theta –2\theta$ and time during the switching of the remnant polarization by a $-18\mathrm{V}$ pulse to the capacitor. (b) Applied voltage as a function of time during polarization switching. (c) X-ray intensity as a function of time plotted from the data of part (a) along the line with $2\theta =34.83°$. Points $\mathit{a}$ and $\mathit{b}$ denote the times of the beginning and end, respectively, of the structural signal associated with polarization reversal. The shift in absolute values of $2\theta$ between Figs. 1, 2 is the difference in the alignment of the x-ray diffractometer.

Figure 3

Time dependence of the x-ray intensities measured with $2\theta =34.83°$ at several positions on the capacitor. Each curve is labeled with the distance from the position of the first measurement. The intensities at each position of the beam are offset vertically.

Figure 4

(a) Polarization switching times in a $20\times 20\mu {\mathrm{m}}^2$ area of the thin film capacitor. The earliest and latest switching times are red and blue, respectively. It was not possible to unambiguously assign switching times to the white areas. (b) Polarization switching time as a function of a distance along the arrows shown in the inset. The solid line is a linear fit giving a $40\mathrm{m}{\mathrm{s}}^{-1}$ domain wall velocity. The error bars correspond to the uncertainty associated with assigning the switching time.