AVS 53rd International Symposium
    Nanometer-scale Science and Technology Thursday Sessions
       Session NS-ThP

Paper NS-ThP8
Imaging and Polarization Dynamics in Ultrathin Ferroelectric PVDF Copolymers by Piezoresponse Force Microscopy

Thursday, November 16, 2006, 5:30 pm, Room 3rd Floor Lobby

Session: Nanoscale Science and Technology Poster Session
Presenter: B.J. Rodriguez, Oak Ridge National Laboratory
Authors: B.J. Rodriguez, Oak Ridge National Laboratory
S. Jesse, Oak Ridge National Laboratory
J. Kim, University of Nebraska
S. Ducharme, University of Nebraska
S.V. Kalinin, Oak Ridge National Laboratory
Correspondent: Click to Email
Ferroelectric polyvinylidene fluoride (PVDF) is widely used as a piezoelectric material because of its outstanding electromechanical properties. High-quality monolayer-thin films of PVDF and its copolymers are fabricated using a Langmuir-Blodgett technique, enabling applications such as all-polymer field effect transistors, polymer ferroelectric random access memories, and flexible ferroelectric electronic components. In order to realize the full potential of PVDF, significant progress must be made in nanoscale characterization of the structure of PVDF films. Here, the local structure, electromechanical activity, and polarization switching of ultrathin ferroelectric films of PVDF copolymers are studied by piezoresponse force microscopy (PFM). PFM imaging of PVDF thin films reveals ferroelectric domain sizes of less than 40 nm at a resolution below 5 nm. The combination of vertical and lateral PFM data reveals that the polar axes of the molecules are not orthogonal to the substrate. Local hysteresis loop measurements and local domain writing are performed to establish the potential of PVDF films for data storage and electronic applications. Unlike traditional ferroelectric thin films, PVDF exhibits switching on the order of milliseconds, which is attributed to a fundamental difference in the switching mechanism as compared to perovskite ferroelectrics. In PVDF, a significant change in molecular geometry, as opposed to dipole switching, is required to change the polarization orientation. To address the dynamic polarization behavior in PVDF, spatially resolved mapping of piezoelectric response is performed using switching spectroscopy PFM (SS-PFM). Lastly, the potential advantages of liquid PFM to minimize surface damage are discussed. These results provide a complementary view of structure, ferroelectric properties, and domain dynamics in PVDF on the nanoscale.