April 29, 2016

Unravelling and controlling hidden imprint fields in ferroelectric capacitors

Fanmao Liu, I. Fina, R. Bertacco, and  J. Fontcuberta

Scientific Reports 6, 25028  (2016) DOI: 10.1038/srep25028

Ferroelectric materials are non-centrosymmetric materials having have a switchable spontaneous polarization that can point along energetically equivalent opposite directions. They form the so-called ferroelectric domains. Associated to the polarization there is an internal electric that needs to be screened to allow persistence of ferroelectric polarization. Photogenerated charge carriers induced by suitable illumination can modify the polarization screening, thus modifying the relative the stability of polar domains. The combination of photoactivity with ferroelectricity can give rise to very interesting features of interest in many technological applications, ranging from data storage and photovoltaics The detailed analysis of the distinct photoactivity present in ferroelectrics is crucial if one want to use it in photovoltaic or other applications

Here we show that in the simplest ferroelectric device: a series connection of identical ferroelectric capacitors the ferroelectric switching of the ferroelectric domains occurs as a single step process (simultaneous switching) or not (independent switching) depending on the measuring conditions and the polarization screening mechanism. We also demonstrate that photoinduced carriers can be used to select the relative stability of the ferroelectric domain and thus data retention in ferroelectric based memory device.

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