Mechanical Writing of Ferroelectric Polarization

• Published in: Science (American Association for the Advancement of Science) Vol. 336; no. 6077; pp. 59 - 61
• Main Authors: Lu, H., Bark, C.-W., de los Ojos, D. Esque, Alcala, J., Eom, C. B., Catalan, G., Gruverman, A.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 06.04.2012; The American Association for the Advancement of Science
• Subjects: Atomic force microscopes; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Deformation; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electric potential; Electrical bias; Electrodes; Exact sciences and technology; Ferroelectric materials; Ferroelectricity; Grants; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Joining; Laboratory Equipment; Load forces; Material films; Materials science; Nanomaterials; Nanostructure; Physics; Piezoelectricity and electromechanical effects; Polarization; Scanning probe microscopes, components and techniques; Structural strain; Thin films; Atomic force microscopy; Polarization; Microscope tips; Ferroelectric materials; Piezoelectric materials; Strain gradient; Electric dipoles; Stress effects; Flexoelectricity; Strong coupling; Nanostructures
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1218693

Ferroelectric materials are characterized by a permanent electric dipole that can be reversed through the application of an external voltage, but a strong intrinsic coupling between polarization and deformation also causes all ferroelectrics to be piezoelectric, leading to applications in sensors and high-displacement actuators. A less explored property is flexoelectricity, the coupling between polarization and a strain gradient. We demonstrate that the stress gradient generated by the tip of an atomic force microscope can mechanically switch the polarization in the nanoscale volume of a ferroelectric film. Pure mechanical force can therefore be used as a dynamic tool for polarization control and may enable applications in which memory bits are written mechanically and read electrically.