A group of scientists has created a new Atomic Force Microscopy mode called “Direct Piezoelectric Force Microscopy (DPFM)”. With this new microscope, piezoelectric materials can be mapped and studied at the nanoscale by employing the direct piezoelectric effect.
The piezoelectric material to study is strained by a sharp tip, an AFM tip with nanometric size. The tip applies a force to the material to study and collects the current that is generated. The amplifier component consists of a Femtoampere Input Bias Current Electrometer Amplifier populated with a 1 TeraOhm resistor as a feedback resistor in a transimpedance configuration. This amplifier converts the current into a voltage signal that can be saved through a Data Acquisition Card (DAC). The amplifier work at a low bandwidth, because both the feedback capacitor and the feedback resistor acts as a filter, limiting the bandwidth. Even with this limitation, the new mode implies an advance into material research.
The AFM is one of the most used characterization techniques thanks to the versatility of this type of microscope: it is not only possible to see the materials, but also to study other properties that could not be measured such as their electrical, magnetic or thermal properties. This versatility has made AFM a far-reaching technique for characterization of materials, which already assumes an industry by itself that reports $ 400 million in profits annually. (ref: http://www.nanotechmag.com/wp-content/uploads/2014/09/SPMicroscopes2014-.pdf).
This new AFM mode enhances this microscopy technique as a standard characterization technique available for material research specifically for the case of piezoelectricity and ferroelectricity.
For more information: Piezo-generated charge mapping revealed through Direct Piezoelectric Force Microscopy, A. Gomez et al. , Nature Communications (2017), DOI: 10.1038/s41467-017-01361-2