arXiv subjects

Benjamin Bein

Publications and source records attributed to Benjamin Bein.

3 recordsLinked to original sources

arXiv2022

Photocatalytic water oxidation on SrTiO$_3$ [001] surfaces

SrTiO$_3$ is a highly efficient photocatalyst for the overall water splitting reaction under UV irradiation. However, an atomic-level understanding of the active surface sites responsible for the oxidation and reduction reactions is still lacking. Here we present a unified experimental and computational account of the photocatalytic activity at the SrO- and TiO$_2$- terminations of aqueous-solvated [001] SrTiO$_3$. Our experimental findings show that the overall water-splitting reaction proceeds on the SrTiO$_3$ surface only when the two terminations are simultaneously exposed to water. Our simulations explain this, showing that the photogenerated hole-driven oxidation primarily occurs at SrO surfaces in a sequence of four single hole transfer reactions, while the TiO$_2$ termination effects the crucial band alignment of the photocatalyst relative to the water oxidation potential. The present work elucidates the interdependence of the two chemical terminations of SrTiO$_3$ surfaces, and has consequent implications for maximizing sustainable solar-driven water splitting.

cond-mat.mtrl-sci↗

arXiv2019

Role of ferroelectric polarization during growth of highly strained ferroelectrics revealed by in-situ x-ray diffraction

Strain engineering of perovskite oxide thin films has proven to be an extremely powerful method for enhancing and inducing ferroelectric behavior. In ferroelectric thin films and superlattices, the polarization is intricately linked to crystal structure, but we show here that it can also play an important role in the growth process, influencing growth rates, relaxation mechanisms, electrical properties and domain structures. We have studied this effect in detail by focusing on the properties of BaTiO$_{3}$ thin films grown on very thin layers of PbTiO$_{3}$ using a combination of x-ray diffraction, piezoforce microscopy, electrical characterization and rapid in-situ x-ray diffraction reciprocal space maps during the growth using synchrotron radiation. Using a simple model we show that the changes in growth are driven by the energy cost for the top material to sustain the polarization imposed upon it by the underlying layer, and these effects may be expected to occur in other multilayer systems where polarization is present during growth. Our research motivates the concept of polarization engineering during the growth process as a new and complementary approach to strain engineering.

cond-mat.mtrl-sci↗

arXiv2015

In-situ x-ray diffraction and the evolution of polarization during the growth of ferroelectric superlattices

In epitaxially strained ferroelectric thin films and superlattices, the ferroelectric transition temperature can lie above the growth temperature. Ferroelectric polarization and domains should then evolve during the growth of a sample, and electrostatic boundary conditions may play an important role. In this work, ferroelectric domains, surface termination, average lattice parameter and bilayer thickness are simultaneously monitored using in-situ synchrotron x-ray diffraction during the growth of BaTiO$_3$/SrTiO$_3$ superlattices on SrTiO$_3$ substrates by off-axis RF magnetron sputtering. The technique used allows for scan times substantially faster than the growth of a single layer of material. Effects of electric boundary conditions are investigated by growing the same superlattice alternatively on SrTiO$_3$ substrates and 20nm SrRuO$_3$ thin films on SrTiO$_3$ substrates. These experiments provide important insights into the formation and evolution of ferroelectric domains when the sample is ferroelectric during the growth process.

cond-mat.mtrl-sci↗