References of "Granzow, Torsten"
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See detailBirefringence induced by antiferroelectric switching in transparent polycrystalline PbZr0.95Ti0.05O3 film
Biswas, Pranab UL; Milesi-Brault, Cosme; Martínez, Alfredo Blázquez et al

in Physical Review Materials (2022), 6(9), 091403

The most characteristic functional property of antiferroelectric materials is the possibility to induce a phase transition from a nonpolar to a polar phase by an electric field. Here, we investigate the ... [more ▼]

The most characteristic functional property of antiferroelectric materials is the possibility to induce a phase transition from a nonpolar to a polar phase by an electric field. Here, we investigate the effect of this field-induced phase transition on the birefringence change of PbZr0.95Ti0.05O3. We use a transparent polycrystalline PbZr0.95Ti0.05O3 film grown on PbTiO3/HfO2/SiO2 with interdigitated electrodes to directly investigate changes in birefringence in a simple transmission geometry. In spite of the polycrystalline nature of the film and its moderate thickness, the field-induced transition produces a sizable effect observable under a polarized microscope. The film in its polar phase is found to behave like a homogeneous birefringent medium. The time evolution of this field-induced birefringence provides information about irreversibilities in the antiferroelectric switching process and its slow dynamics. The change in birefringence has two main contributions: One that responds briskly and a slower one that rises and saturates over a period of as long as 30 min. Possible origins for this long saturation and relaxation times are discussed. [less ▲]

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See detailIncreasing bulk photovoltaic current by strain tuning
Nadupalli, Shankari; Kreisel, Jens UL; Granzow, Torsten

in Science Advances (2019), 5(3),

Photovoltaic phenomena are widely exploited not only for primary energy generation but also in photocatalytic, photoelectrochemistry, or optoelectronic applications. In contrast to the interface-based ... [more ▼]

Photovoltaic phenomena are widely exploited not only for primary energy generation but also in photocatalytic, photoelectrochemistry, or optoelectronic applications. In contrast to the interface-based photovoltaic effect of semiconductors, the anomalous or bulk photovoltaic effect in ferroelectrics is not bound by the Shockley-Queisser limit and, thus, can potentially reach high efficiencies. Here, we observe in the example of an Fe-doped LiNbO3 bulk single crystal the existence of a purely intrinsic ``piezophotovoltaic'' effect that leads to a linear increase in photovoltaic current density. The increase reaches 75 under a low uniaxial compressive stress of 10 MPa, corresponding to a strain of only 0.005\%. The physical origin and symmetry properties of the effect are investigated, and its potential for strain-tuned efficiency increase in nonconventional photovoltaic materials is presented. [less ▲]

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