Publication Type:Journal Article
Source:Applied Physics Letters, Volume 86, Number 26, p.1-3 (2005)
Keywords:Capacitors, Correlation methods, crystal orientation, Crystallographic orientations, electric potential, electrodes, Ferroelectric materials, Ferroelectric random access memory (FRAM), Grain boundaries, Metallorganic chemical vapor deposition, Nanoscale polarization relaxation, Piezoresponse force microscopy (PFM) images, Polycrystalline materials, thin films, X ray diffraction analysis
In this letter, we report on the study of nanoscale polarization relaxation phenomena in polycrystalline PbZr0.4 Ti0.6 O3 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. © 2005 American Institute of Physics.
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