Abstract
In perovskite oxide ferroelectrics, gradients of lattice strain are known to induce nanoscale topological structures, leading to novel or enhanced functionality. Here, we experimentally detect and theoretically analyze thickness distribution of structural properties in epitaxial ${\mathrm{Pb}}_{0.5}{\mathrm{Sr}}_{0.5}\mathrm{Ti}{\mathrm{O}}_{3}$ films grown on (001) $\mathrm{SrTi}{\mathrm{O}}_{3}$ substrates. We show that the relaxation of substrate-imposed stress produces a strain gradient, which leads to the formation of distinct ferroelectric phases as a function of distance from the film-substrate interface within the same film. Charge carriers trapped at phase boundaries stabilize the induced phases and manifest themselves under electric field. Crosstalk between the phases, where polarization may rotate in one phase and invert in the other one, opens perspectives for advanced ferroelectric thin film devices.
Highlights
Recent demand for nanotechnology has made nanoscale material science and physics critical areas of research
We show that the relaxation of substrate-imposed stress produces a strain gradient, which leads to the formation of distinct ferroelectric phases as a function of distance from the film-substrate interface within the same film
The structure of the PSTO/SRO/STO thin films was first analyzed with x-ray diffraction (XRD)
Summary
Recent demand for nanotechnology has made nanoscale material science and physics critical areas of research. With our limited intuition for the nanoworld, understanding the structure-property relations often lags behind technological advances. Thin films of perovskite oxide ferroelectrics are good examples of this, where advances in technology and research tools have opened horizons for experimental explorations, enabling progress in modeling and understanding [1,2,3]. Perovskite oxide ferroelectrics are widely studied for their diverse functionalities, including switchable polarization, piezoelectricity, high-dielectric susceptibility, pyroelectricity, electro-optics, and other effects that are essential for practical applications. Strain can efficiently enhance or tune major functional properties that are key for applications in actuation or sensing [9,10], optics [11], and memory [12], to name a few
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