ABSTRACT
Since the discovery of ferroelectricity a century ago, ferroelectrics have made their way into countless applications that exploit their superior pyroelectric and piezoelectric properties, large dielectric permittivities, non-linear optical response, and their defining property—the switchable polarisation. 100 years on and these materials remain as exciting as ever, continuing to challenge our fundamental understanding and offering novel solutions for future low-power electronics. Recent discoveries of unexpected properties at ferroelectric domain boundaries have led to the emergence of the field of ‘domain-wall nanoelectronics’, where the domain walls, which are easily created or destroyed, act as the functional elements in reconfigurable devices. The properties of ferroelectrics also change dramatically when their dimensions are reduced, motivating intense activity on nanoscale ferroelectricity. The enhanced sensitivity of ultrathin ferroelectrics to the mechanical and electrostatic boundary conditions, which can be effectively manipulated in epitaxial heterostructures, enables the design of artificially layered ferroelectrics with unusual and topologically interesting polarization patterns that are unattainable in the bulk materials. The dense nanoscale stripe domains, polar bubbles, skyrmions and merons, or the highly ordered ‘domain supercrystals’ produced in this way are not only interesting in their own right, but also have profound effects on the functional properties of these synthetic materials, sometimes leading to unusual phenomena, as exemplified by the negative capacitance effect [1-3].
In this talk, we will explore how electrostatic and strain engineering can be used to create different polarization patterns in strained and free-standing ferroelectric oxide superlattices, discussing their characterization using a combination of X-ray diffraction, scanning probe microscopy and electron microscopy, and the effect they have on the physical properties of these artificially layered materials.
[1] M. Hadjimichael et al., Nature Materials 20, 495 (2021).
[2] P. Zubko et al., Nature 534, 524 (2016).
[3] J. Iñiguez et al. Nature Reviews Materials 4, 243 (2019).
BIOGRAPHY
Prof. Pavlo Zubko is currently a Professor of Physics in the Department of Physics and Astronomy, University College London, and a PI at the London Centre for Nanotechnology. After completing a degree in Natural Sciences, he stayed on at Cambridge University for a PhD, studying ferroelectric thin films and flexoelectricity in bulk strontium titanate. He then held a postdoctoral position at the University of Geneva, where he became fascinated by epitaxial oxide heterostructures, working on ferroelectric superlattices and rare-earth nickelates. In 2013, he took up a lectureship at University College London, and has become a Professor now. The main focus of his current research is on nanoscale ferroelectricity in ferroelectric thin films and multilayers. His group uses a range of experimental techniques to investigate nanoscale domain structures and their effect on the functional properties of ferroelectrics, including unusual phenomena such as negative capacitance.
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