Nanoscale polarization relaxation in a polycrystalline ferroelectric thin film: Role of local environments

Authors

V. Nagarajan, University of New South Wales, Sydney
S. Aggarwal, Texas Instruments Incorporated, 13560 North Central Expressway, MS 3736 Dallas, Texas
Alexei Gruverman, University of Nebraska-LincolnFollow
R. Ramesh, University of California, at Berkeley
R. Waser, Institute for Solid State Physics and CNI, Forschungszentrum Juelich, D 52425 Germany

Date of this Version

June 2005

Comments

Published in Appl. Phys. Lett. 86, 262910 2005. Copyright © 2005 American Institute of Physics. Used by permission.

Abstract

In this letter, we report on the study of nanoscale polarization relaxation phenomena in polycrystalline PbZr_0.4Ti_0.6O₃ films. Piezoresponse force microscopy (PFM) images of the as-grown sample reveal grains with a range of contrast, from fully white to gray to fully black. It is shown that this local change in the contrast (magnitude) of the piezoresponse from grain to grain can be attributed to the crystallographic orientation within each grain. PFM-based relaxation experiments show that the rate of relaxation is different for each grain, furthermore it is strongly dependent on the tilt of individual crystallographic orientation with respect to the polar axis. Strongly tilted away nonpolar axis grains show a much stronger decay of the polarization compared to polar axis-oriented grains. Therefore, for an ensemble of grains under a common top electrode, the relaxation events would first take place in grains, which are nonpolar axis oriented.