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Univ. Paris-Saclay
Strain and electrostatic engineering of polarization patterns in artificially layered ferroelectrics
London Centre for Nanotechnology
Mercredi 04/12/2019, 11:00-12:15
SPEC Salle Itzykson, Bât.774, Orme des Merisiers

Since their discovery almost 100 years ago, ferroelectrics have made their way into countless applications that reply on their superior piezoelectric, pyroelectric, dielectric and optical properties. Yet despite a century of research, these materials continue to surprise, and their technological potential seems far from being exhausted. Recent research reveals that domain walls in ferroelectrics can host unexpected properties such as enhanced conductivity, magnetism and unusual polarization arrangements. At the same time, the properties of ferroelectrics change dramatically when their dimensions are reduced, motivating an intense activity on nanoscale ferroelectricity. In this context, epitaxial heterostructures consisting of ferroelectric oxides have emerged as a fascinating playground for discovering exotic polarization configurations that are not accessible in bulk materials. The behaviour of ultrathin ferroelectrics is determined largely by the mechanical and electrostatic boundary conditions, which can be effectively manipulated, enabling the realization of materials with tailored polarization structures and unusual properties.
In this seminar, we will discuss how the electrostatic boundary conditions at interfaces in ferroelectric-dielectric superlattices lead to the formation of highly inhomogeneous polarization arrangements ranging from dense stripe domains to polar bubbles and skyrmion-like patterns. Such polarization structures have a profound effect on the dielectric response of these artificially layered materials and give rise to the so-called negative capacitance behaviour that could help to reduce the power consumption of field effect transistors.
We will explore how ferroelastic domain arrangements can be controlled through substrate-imposed epitaxial strain and how their switching behaviour can be imaged using synchrotron X-ray nanodiffraction.
Finally, we will show how both electrostatic and mechanical boundary conditions can be exploited to generate a domain crystal—a 3-dimensionally ordered hierarchical domain structure—in metal-ferroelectric superlattices.
Coffee and pastries at 11h00.


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