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Unravelling and controlling hidden imprint fields in ferroelectric capacitors.

ABSTRACT: Ferroelectric materials have a spontaneous polarization that can point along energetically equivalent, opposite directions. However, when ferroelectric layers are sandwiched between different metallic electrodes, asymmetric electrostatic boundary conditions may induce the appearance of an electric field (imprint field, Eimp) that breaks the degeneracy of the polarization directions, favouring one of them. This has dramatic consequences on functionality of ferroelectric-based devices such as ferroelectric memories or photodetectors. Therefore, to cancel out the Eimp, ferroelectric components are commonly built using symmetric contact configuration. Indeed, in this symmetric contact configuration, when measurements are done under time-varying electric fields of relatively low frequency, an archetypical symmetric single-step switching process is observed, indicating Eimp???0. However, we report here on the discovery that when measurements are performed at high frequency, a well-defined double-step switching is observed, indicating the presence of Eimp. We argue that this frequency dependence originates from short-living head-to-head or tail-to-tail ferroelectric capacitors in the device. We demonstrate that we can modulate Eimp and the life-time of head-to-head or tail-to-tail polarization configurations by adjusting the polarization screening charges by suitable illumination. These findings are of relevance to understand the effects of internal electric fields on pivotal ferroelectric properties, such as memory retention and photoresponse.

SUBMITTER: Liu F

PROVIDER: S-EPMC4848548 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Unravelling and controlling hidden imprint fields in ferroelectric capacitors.

Liu Fanmao F Fina Ignasi I Bertacco Riccardo R Fontcuberta Josep J

Scientific reports 20160428

Ferroelectric materials have a spontaneous polarization that can point along energetically equivalent, opposite directions. However, when ferroelectric layers are sandwiched between different metallic electrodes, asymmetric electrostatic boundary conditions may induce the appearance of an electric field (imprint field, Eimp) that breaks the degeneracy of the polarization directions, favouring one of them. This has dramatic consequences on functionality of ferroelectric-based devices such as ferr ...[more]

PMID: 27122309

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Project description:Chloroplast is a major plant cell organelle that fulfills essential metabolic and biosynthetic functions. Located at the interface between the chloroplast and other cell compartments, the chloroplast envelope system is a strategic barrier controlling exchanges of ions, metabolites and proteins, thus regulating essential metabolic functions (synthesis of hormones precursors, amino acids, pigments, sugars, vitamins, lipids, nucleotides…) of the plant cell. However, chloroplast envelope membranes remain the hidden part of the chloroplast proteome and many envelope proteins remain to be characterized (known but uncharacterized envelope proteins) or identified (orphan known envelope-associated functions carried by unidentified proteins) Indeed, the envelope contains only 1% of the chloroplast proteins (i.e. 0.25% of the whole cell proteome). When comparing the composition crude leaf extract and purified envelope vesicles, a high theoretical enrichment factor (EF) of specific envelope proteins is thus expected. This is especially true for minor envelope proteins (e.g. representing 1/100 or 1/1000 of the envelope protein content). Sensitivity of MS technique has been greatly improved during the last decade. Today, thanks to the continuous improvement of MS techniques, we are able to detect more components in a complex sample, to generate quantitative data and to statistically validate above-cited enrichment factor. Here, we have taken advantage of present-days better MS sensitivity towards a better definition (differentiate genuine envelope proteins from contaminants) of the chloroplast envelope proteome. This MS- and statistical-based analysis relied on an enrichment factor calculated for each protein identified in purified envelope fractions when compared to the value obtained for the same protein in crude cell extracts. Using this approach, a total of 1376 proteins was detected in purified envelope fractions, of which, more than 500 could be assigned an envelope localization combining MS-based statistical analyses and manual annotation using data from the literature or prediction tools. Interestingly, many of such proteins being unknown or unexpected envelope components, these data constitute a new resource of significant value to the broader plant science community aiming to define principles and molecular mechanisms controlling fundamental aspects of plastid biogenesis and functions.

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Unravelling and controlling hidden imprint fields in ferroelectric capacitors.

Publications

Unravelling and controlling hidden imprint fields in ferroelectric capacitors.

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