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Tip-induced mechanical polarization control in P(VDF-TRFE) ferroelectric polymer films

When Jul 03, 2018
from 02:30 PM to 03:00 PM
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R. Roth,1 M. Koch,1 J. Schaab,2 M. Lilienblum,2 T. Thurn-Albrecht,1 K. Dörr1*

1 Institute of Physics, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
2 Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland

The ferroelectric copolymer P(VDF-TrFE) is the most often used non-ceramic piezoelectric material due to its substantial piezoelectricity (-d33 = 30-35 pm/V) and advantageous properties like biocompatibility, flexibility, low-cost processing. However, disorder of electric dipole orientations in films and fibers is often strong and suppresses the achievable electric and mechanical responses. We introduce an approach for controlling the polarization alignment in thin films which have four local polarization orientations. It is based on applying soft, non-destructive mechanical pressure with a force-microscopy tip to vertically poled areas. Micron-sized ferroelectric domains with well-defined polarization orientation and low surface roughness have been written resulting in a multiplication of the original piezoresponse. Further, nanoscale in-plane domain patterns can be written. Our observations point towards a tip-induced ferroelastic switching mechanism (in contrast to the presently much investigated flexoelectric switching). Exploiting such mechanical polarization alignment could advance the performance of various devices based on piezoelectricity, especially those relying on in-plane strains or polarization.

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The study of functional materials has underpinned the enormous changes in information technology and electronic systems seen in the past decades. Research in the Department on device materials spans many of the most exciting areas in which the functional properties of new materials are being understood and developed.