This title appears in the Scientific Report :
2006
Please use the identifier:
http://hdl.handle.net/2128/2491 in citations.
Piezoresponse force microscopy and surface effects of perovskite ferroelectric nanostructures
Piezoresponse force microscopy and surface effects of perovskite ferroelectric nanostructures
With the advancing miniaturization of ferroelectric, non-volatile memories, the question arises how the spontaneous polarization and the displacement current scale with size. Piezoresponse Force Microscopy (PFM) is the method of choice to study these properties. Notwithstanding the huge success of t...
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Personal Name(s): | Peter, Frank (Corresponding author) |
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Contributing Institute: |
Center of Nanoelectronic Systems for Information Technology; CNI Elektronische Materialien; IFF-IEM |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2006
|
Physical Description: |
106 S. |
Dissertation Note: |
RWTH Aachen, Diss., 2006 |
ISBN: |
3-89336-444-7 |
Document Type: |
Book Dissertation / PhD Thesis |
Research Program: |
Grundlagen für zukünftige Informationstechnologien |
Series Title: |
Schriften des Forschungszentrums Jülich. Reihe Informationstechnik / Information Technology
11 |
Subject (ZB): | |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
With the advancing miniaturization of ferroelectric, non-volatile memories, the question arises how the spontaneous polarization and the displacement current scale with size. Piezoresponse Force Microscopy (PFM) is the method of choice to study these properties. Notwithstanding the huge success of this method, many aspects of the contrast formation mechanisms are not yet understood. The aim of this work is a systematic investigation of the intrinsic and extrinsic contributions to PFM measurements of ferroelectric nanostructures. X-Ray Photoelectron Spectroscopy and PFM measurements confirm that perovskite ferroelectrics are covered by adsorbates under ambient conditions. In PFM this leads to a severe reduction of the electric field applied to the sample and attenuates the piezoresponse by up to one order of magnitude. Heat treatment in high vacuum is successfully employed to lessen the amount and impact of adsorbates and to substantially recover the piezoresponse. Due to the cantilever geometry the optical amplification for the in-plane response is about 20 times larger than for the out-of-plane response. This large optical amplification makes the in-plane piezoresponse measurements highly attractive. However, in $\textit{c}$-axis oriented thin films no in-plane piezoresponse should be detected at all due to the radial potential distribution underneath the tip. Measurements and simulations are presented showing that an in-plane response can be detected whenever the radial symmetry is broken. This can be due to an asymmetric cantilever, local variations of material parameters or an uneven surface. Especially on the slopes of ferroelectric nanoislands, the topography has a significant influence on the in-plane PFM signal. As a result of the broken symmetry of the radial potential distribution and the unbalanced amount of material underneath the tip a significant enhancement of the in-plane response occurs at the perimeter even of $\textit{c}$-axis oriented grains. Due to the cantilever geometry, this enhancement is restricted to slopes of the grain parallel to the axis of the cantilever. However, the enhancement may also be observed on the slopes perpendicular to the cantilever-axis in out-of-plane measurements as a result of a mechanical crosstalk. Another kind of crosstalk originates from a misalignment of the cantilever with respect to the four sector photo diode. In this case the pronounced in-plane response supersedes the outof- plane signal and in some lateral force microscopy configurations this may even result in the in-plane signal impacting the $\textit{z}$-feedback-loop of the Atomic Force Microscope. A novel mechanical compensation scheme is suggested to eliminate this crosstalk. Similar to other imaging measurement techniques, PFM suggests a very intuitive access to the acquired data. In this sense the present work addresses new critical aspects of the measurement technique with an emphasis on the tip-sample interaction in the presence of adsorbates. |