AVS 50th International Symposium
    Nanometer Structures Wednesday Sessions
       Session NS-WeM

Paper NS-WeM3
Quantitative Imaging of Local Electromechanical Properties of Ferroelectric Surfaces by Piezoresponse Force Microscopy

Wednesday, November 5, 2003, 9:00 am, Room 308

Session: Nanomechanics
Presenter: S.V. Kalinin, Oak Ridge National Laboratory
Authors: S.V. Kalinin, Oak Ridge National Laboratory
J. Shin, University of Tennessee
A.P. Baddorf, Oak Ridge National Laboratory
J.F. Wendelken, Oak Ridge National Laboratory
M. Kachanov, Tufts University
E. Karapetian, Tufts University
Correspondent: Click to Email
Piezoresponse Force Microscopy has become the primary tool for the characterization of ferroelectric materials at nanoscale dimensions. Application of a periodic bias to the AFM tip in contact with the surface results in surface oscillations due to an inverse piezoelectric effect. These are detected with a lock-in amplifier to produce PFM amplitude and phase images. Special attention has been attracted to the potential of this technique for local spectroscopic measurements, i.e. the local electromechanical hysteresis loop of the material. Application of a dc bias or force to the tip can switch the local polarization, opening possibilities of PFM as a nanolithographic tool. Despite extensive effort, a detailed understanding of PFM imaging, including tip induced mechanical and electrostatic phenomena inside the ferroelectric, has not previously been achieved. Here, the analytical solution of the coupled electromechanical problem for piezoelectric indentation is used to derive the electric field and strain distribution inside the ferroelectric material, providing a complete continuum mechanical description of the PFM imaging mechanism. These solutions are used to quantitatively interpret PFM spectroscopic measurements and bias- and stress-induced domain behavior. It is shown that the dielectric gap formation at the tip surface junction due to surface contamination significantly affects the PFM imaging mechanism. Preliminary results of PFM imaging under controlled atmosphere and UHV conditions are presented.