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3D composition mapping obtained from the new DPFM mode. Both the electrogenerated charge and the electromechanical behavior are obtained for a sample composed of Periodically Poled Lithium Niobate.

Abstract:
A team of researchers have created a new Atomic Force Microscope called “Direct Piezoelectric Force Microscopy” (DPFM). In particular, they measure the tiny currents produced by the piezoelectric effect with a transimpedance amplifier, which consists into a current-to-voltage converter. The work entitles “Piezo-generated charge mapping revealed through direct piezoelectric force microscopy” published in the prestigious scientific journal Nature Communications.

New Atomic Force Microscope to study piezoelectrics at the nanoscale

Barcelona, Spain | Posted on October 29th, 2017

In this particular research, the material is stressed by the AFM tip with nanometric size. The tip applies a force in the range of hundreds of microNewton and measures the generated charge that is created into the material. The new mode was proved by characterizing several common ferroelectric materials: A Periodically Poled Lithium Niobate, Bismuth Ferrite and different Lead Zirconate Titanate. The mode is employed in standard constant force contact mode AFM, by using a solid platinum tip with part number RMN-25Pt200H. As the mapping is performed in constant mode, the amplifier gives zero signal while scanning a single domain, however, where the tip crosses a domain, a current is generated as a consequence of the inversion of the generated charge. The researchers are able to integrate the current obtained in order to estimate the generated charge by the material. The charges recorded are 5fC for Periodically Poled Lithium Niobate, 25 fC for Bismuth Ferrite and 90fC for Lead Zirconate Tantalate. Just few quantities are really quantitative in AFM, being one of them the force applied by the tip. By known the force and integrating the current generated, researchers are able to estimate the d33 piezoelectric constant of the materials scanned. Force-vs-distance curves where the tip is placed in one spot and the force applied is changed through a constant force rate applied. By performing such experiments, researchers are able to distinguish between down and up domains, and it opens a window into made spectroscopy experiments quantitative.

The research focused into the mapping of Piezogenerated charge of a piezoelectric material. Piezoelectricity is a property where a charge is generated by a material as a consequence of a mechanical stress applied to the material. In this particular research, the material is stressed by a tiny needle, an AFM tip with nanometric size. The tip applied a force in the range of 100 microNewton and measures the generated charge that is created into the material. The total charge collected for each material was 5fC for Periodically Poled Lithium Niobate, 25 fC for Bismut Ferrite and 90fC for Lead Zirconate Titanate. This new mode enhances Atomic Force Microscopy as a key future technique available for material research and opens a future into counting electrons at the nanoscale.

“More info: Piezo-generated charge mapping revealed through Direct Piezoelectric Force Microscopy, A. Gomez et al. , Nature Communications (2017), DOI: 10.1038/s41467-017-01361-2”

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Campus de la Universitat Autònoma de Barcelona
08193 Bellaterra, Catalunya, Espanya
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