Abstract
Complex-oxide superlattices (SLs) with atomic-scale periodicity have dynamical properties that are distinct from thin films of uniform composition. The origins of these properties are closely related to the dynamics of polarization domains and to field-driven changes in the symmetries resulting from interfacial coupling between different components. These dynamics are apparent at timescales from a few nanoseconds to several milliseconds in experiments probing the piezoelectricity of a ferroelectric/dielectric BaTiO3(BTO)/CaTiO3 (CTO) SL using time-resolved x-ray microdiffraction. At the 100 ns timescale, the piezoelectric distortion is approximately ten times smaller than in the millisecond regime. This reduced piezoelectricity at short timescales is not observed in previously studied PbTiO3/SrTiO3 SLs or compositionally uniform ferroelectrics such as tetragonal compositions of Pb(Zr,Ti)O3. The unusual behavior of the BTO/CTO SL can be linked to the switching of a nanodomain state into a uniform polarization state or to a field-induced crystallographic symmetry transition. A comparison of the results with the characteristic timescales of these two dynamical phenomena in other complex oxides with different compositions suggests that the phase transition is a more likely possibility.
Highlights
Millisecond- and nanosecond-duration time-resolved x-ray microdiffractionTime-resolved x-ray microdiffraction studies of the BTO/CTO SL were conducted at the Advanced Photon Source (APS) using the experimental arrangement shown in figure 1
Complex-oxide superlattices (SLs) with atomic-scale periodicity have dynamical properties that are distinct from thin films of uniform composition
The competition between these structural effects in SLs plays a key role in determining the equilibrium crystallographic symmetry and has a strong influence on ferroelectric properties [7, 10]. Both the direction and magnitude of polarization in SL are hypothesized to be susceptible to field-induced transitions between antiferrodistortive symmetries and more highly polar ferroelectric states [11,12,13]. These field-induced symmetry transitions are conceptually similar to those in relaxor ferroelectrics, ferroic materials near a morphotropic phase boundary and ferroelectrics governed by the polarization–rotation mechanism [14, 15], in that the electric field can be sufficient to move the system between the states with different symmetries
Summary
Time-resolved x-ray microdiffraction studies of the BTO/CTO SL were conducted at the Advanced Photon Source (APS) using the experimental arrangement shown in figure 1. A second series of measurements with nanosecond time resolution were carried out at station 7-IDB of the APS. Electrical pulses corresponding to photons detected by the APD were gated by digital electronics to select photons scattered from x-ray bunches with the desired time relationship to the applied electric field. The data acquisition consisted of 5000 (figures 2, 4 and 5) or 9999 (figure 7) repetitions of the electric field pulses in order to achieve sufficient counting statistics. The 300 ns duration of the electric field in the pulsed measurements was greater than the 153 ns interval between x-ray bunches in the operating mode of the APS used in this study. In order to speed up the data acquisition, the experimental circuitry recorded the intensities from three sequential x-ray bunches and three diffraction patterns simultaneously at three different time points separated by 153 ns. Overlapping time points resulting from the use of the series of x-ray bunches appear in the data and serve as a measure of the reproducibility of the measurement
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
