AVS 53rd International Symposium
    Nanometer-scale Science and Technology Monday Sessions
       Session NS-MoM

Paper NS-MoM10
Electromechanical Imaging of Ferroelectric Materials in a Liquid Environment: Ultrahigh Resolution and Novel Physics

Monday, November 13, 2006, 11:00 am, Room 2016

Session: Nanoscale Imaging Techniques
Presenter: S.V. Kalinin, Oak Ridge National Laboratory
Authors: B.J. Rodriguez, Oak Ridge National Laboratory
S. Jesse, Oak Ridge National Laboratory
A.P. Baddorf, Oak Ridge National Laboratory
S.V. Kalinin, Oak Ridge National Laboratory
B. Mirman, Suffolk University
E.A. Eliseev, National Academy of Science of Ukraine
A.N. Morozovska, National Academy of Science of Ukraine
Correspondent: Click to Email
High resolution imaging of ferroelectric materials is demonstrated using piezoresponse force microscopy (PFM) in an aqueous environment. In the last decade, PFM has been established as a powerful tool for nanoscale imaging, spectroscopy, domain patterning and lithography of ferroelectric thin films, as well as the characterization of capacitors used for ferroelectric memories and data storage. Recent work has demonstrated the applicability of PFM to biological systems where it is possible to image structural properties and molecular orientation with a sub-10 nm resolution. The primary factors limiting the resolution and sensitivity of PFM are electrostatic contributions to the signal and capillary forces. Here, we performed PFM in an aqueous environment to simultaneously minimize both the electrostatic and capillary interactions. A resolution on the order of 1-3 nm, approaching the theoretical domain wall width, as compared to a resolution of ~30 nm in ambient, is reported. The dynamic behavior of the cantilever was analyzed using conventional amplitude-frequency and 2D amplitude-frequency-bias spectroscopy. It is shown that the cantilever dynamics in liquid are significantly different from ambient conditions due to the higher viscosity and added mass effects. Imaging at frequencies corresponding to high-order cantilever resonances is shown to minimize these effect thus allowing sensitivities comparable to ambient conditions. The absence of both long-range electrostatic forces and capillary interactions results in the localization of the ac field to the tip-surface junction and allows the tip-surface contact area to be controlled. This unusual mechanism enables spatial resolutions approaching the intrinsic domain wall width. PFM in liquids will provide novel opportunities for high-resolution studies of ferroelectric materials, imaging of soft polymer materials, and the study of biological systems in physiological environments on, ultimately, the molecular level.