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Le Phuong
Hoang
,
David
Pesquera
,
Gerard N.
Hinsley
,
Robert
Carley
,
Laurent
Mercadier
,
Martin
Teichmann
,
Elena Martina
Unterleutner
,
Daniel
Knez
,
Martina
Dienstleder
,
Saptam
Ganguly
,
Teguh Citra
Asmara
,
Giacomo
Merzoni
,
Sergii
Parchenko
,
Justine
Schlappa
,
Zhong
Yin
,
José Manuel
Caicedo Roque
,
José
Santiso
,
Irena
Spasojevic
,
Cammille
Carinan
,
Tien-Lin
Lee
,
Kai
Rossnagel
,
Jorg
Zegenhagen
,
Gustau
Catalan
,
Ivan A.
Vartanyants
,
Andreas
Scherz
,
Giuseppe
Mercurio
Open Access
Abstract: A fundamental understanding of the interplay between lattice structure, polarization and electrons is pivotal to the optical control of ferroelectrics. The interaction between light and matter enables the remote and wireless control of the ferroelectric polarization on the picosecond timescale, while inducing strain, i.e., lattice deformation. At equilibrium, the ferroelectric polarization is proportional to the strain, and is typically assumed to be so also out of equilibrium. Decoupling the polarization from the strain would remove the constraint of sample design and provide an effective knob to manipulate the polarization by light. Here, upon above-bandgap laser excitation of the prototypical ferroelectric BaTiO3, we induce and measure an ultrafast decoupling between polarization and strain that begins within 350 fs, by softening Ti-O bonds via charge transfer, and lasts for several tens of picoseconds. We show that the ferroelectric polarization out of equilibrium is mainly determined by photoexcited electrons, instead of the strain.
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Aug 2025
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[27468]
Open Access
Abstract: Understanding the mechanisms underlying a stable polarization at the surface of ferroelectric thin films is of particular importance both from a fundamental point of view and to achieve control of the surface polarization itself. In this study, we demonstrate that the X-ray standing wave technique allows the surface polarization profile of a ferroelectric thin film, as opposed to the average film polarity, to be probed directly. The X-ray standing wave technique provides the average Ti and Ba atomic positions, along the out-of-plane direction, near the surface of three differently strained
thin films. This technique gives direct access to the local ferroelectric polarization at and below the surface. By employing X-ray photoelectron spectroscopy, a detailed overview of the oxygen-containing species adsorbed on the surface is obtained. The different amplitude and orientation of the local ferroelectric polarizations are associated with surface charges attributed to different type, amount and spatial distribution of the oxygen-containing adsorbates.
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Oct 2024
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[27468]
Abstract: Ferroelectric materials consist of noncentrosymmetric unit cells with permanent electric
dipole moments leading to a macroscopic spontaneous electric polarization. Uncompensated
charge at the surface of a ferroelectric material is responsible for its chemical reactivity and
can influence the polarization itself. Therefore, revealing the polarization at (and near) the
surface of a ferroelectric material is important not only from a fundamental point of view,
but also to obtain a deeper insight into its surface chemistry and learn how to exploit it for
technologically relevant catalytic reactions [1].
In this study, we investigated BaTiO3
ferroelectric thin films grown on three different
scandate substrates, with a bottom electrode (SrRuO3) in between. The interference
between the incident and Bragg-diffracted X-ray wave generates an X-ray standing wave
(XSW) [2]. The structural sensitivity of the XSW technique combined with the chemical
specificity of X-ray photoemission spectroscopy (XPS) reveals the atomic positions of Ba and
Ti atoms within the top unit cells. As a result, the off-center displacement of Ti atoms, thus
the local ferroelectric polarization, can be determined at different depths from the surface.
These results are discussed in the light of oxygen-related adsorbates measured by XPS.
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Jul 2023
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Nanna
Zhou Hagström
,
Michael
Schneider
,
Nico
Kerber
,
Alexander
Yaroslavtsev
,
Erick
Burgos Parra
,
Marijan
Beg
,
Martin
Lang
,
Christian M.
Günther
,
Boris
Seng
,
Fabian
Kammerbauer
,
Horia
Popescu
,
Matteo
Pancaldi
,
Kumar
Neeraj
,
Debanjan
Polley
,
Rahul
Jangid
,
Stjepan B.
Hrkac
,
Sheena K. K.
Patel
,
Sergei
Ovcharenko
,
Diego
Turenne
,
Dmitriy
Ksenzov
,
Christine
Boeglin
,
Marina
Baidakova
,
Clemens
Von Korff Schmising
,
Martin
Borchert
,
Boris
Vodungbo
,
Kai
Chen
,
Chen
Luo
,
Florin
Radu
,
Leonard
Müller
,
Miriam
Martínez Flórez
,
André
Philippi-Kobs
,
Matthias
Riepp
,
Wojciech
Roseker
,
Gerhard
Grübel
,
Robert
Carley
,
Justine
Schlappa
,
Benjamin E.
Van Kuiken
,
Rafael
Gort
,
Laurent
Mercadier
,
Naman
Agarwal
,
Loïc
Le Guyader
,
Giuseppe
Mercurio
,
Martin
Teichmann
,
Jan Torben
Delitz
,
Alexander
Reich
,
Carsten
Broers
,
David
Hickin
,
Carsten
Deiter
,
James
Moore
,
Dimitrios
Rompotis
,
Jinxiong
Wang
,
Daniel
Kane
,
Sandhya
Venkatesan
,
Joachim
Meier
,
Florent
Pallas
,
Tomasz
Jezynski
,
Maximilian
Lederer
,
Djelloul
Boukhelef
,
Janusz
Szuba
,
Krzysztof
Wrona
,
Steffen
Hauf
,
Jun
Zhu
,
Martin
Bergemann
,
Ebad
Kamil
,
Thomas
Kluyver
,
Robert
Rosca
,
Michał
Spirzewski
,
Markus
Kuster
,
Monica
Turcato
,
David
Lomidze
,
Andrey
Samartsev
,
Jan
Engelke
,
Matteo
Porro
,
Stefano
Maffessanti
,
Karsten
Hansen
,
Florian
Erdinger
,
Peter
Fischer
,
Carlo
Fiorini
,
Andrea
Castoldi
,
Massimo
Manghisoni
,
Cornelia Beatrix
Wunderer
,
Eric E.
Fullerton
,
Oleg G.
Shpyrko
,
Christian
Gutt
,
Cecilia
Sanchez-Hanke
,
Hermann A.
Dürr
,
Ezio
Iacocca
,
Hans T.
Nembach
,
Mark W.
Keller
,
Justin M.
Shaw
,
Thomas J.
Silva
,
Roopali
Kukreja
,
Hans
Fangohr
,
Stefan
Eisebitt
,
Mathias
Kläui
,
Nicolas
Jaouen
,
Andreas
Scherz
,
Stefano
Bonetti
,
Emmanuelle
Jal
Open Access
Abstract: The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, results from the first megahertz-repetition-rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL are presented. The experimental capabilities that the SCS instrument offers, resulting from the operation at megahertz repetition rates and the availability of the novel DSSC 2D imaging detector, are illustrated. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative, providing an ideal test-bed for operation at megahertz rates. Our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range.
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Nov 2022
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Metrology
Optics
|
Giuseppe
Mercurio
,
Jaromír
Chalupský
,
Ioana-Theodora
Nistea
,
Michael
Schneider
,
Věra
Hájková
,
Natalia
Gerasimova
,
Robert
Carley
,
Michele
Cascella
,
Loïc
Le Guyader
,
Laurent
Mercadier
,
Justine
Schlappa
,
Kiana
Setoodehnia
,
Martin
Teichmann
,
Alexander
Yaroslavtsev
,
Tomáš
Burian
,
Vojtĕch
Vozda
,
Luděk
Vyšín
,
Jan
Wild
,
David
Hickin
,
Alessandro
Silenzi
,
Marijan
Stupar
,
Jan
Torben Delitz
,
Carsten
Broers
,
Alexander
Reich
,
Bastian
Pfau
,
Stefan
Eisebitt
,
Daniele
La Civita
,
Harald
Sinn
,
Maurizio
Vannoni
,
Simon G.
Alcock
,
Libor
Juha
,
Andreas
Scherz
Open Access
Abstract: A real-time and accurate characterization of the X-ray beam size is essential to enable a large variety of different experiments at free-electron laser facilities. Typically, ablative imprints are employed to determine shape and size of µm-focused X-ray beams. The high accuracy of this state-of-the-art method comes at the expense of the time required to perform an ex-situ image analysis. In contrast, diffraction at a curved grating with suitably varying period and orientation forms a magnified image of the X-ray beam, which can be recorded by a 2D pixelated detector providing beam size and pointing jitter in real time. In this manuscript, we compare results obtained with both techniques, address their advantages and limitations, and demonstrate their excellent agreement. We present an extensive characterization of the FEL beam focused to ≈1 µm by two Kirkpatrick-Baez (KB) mirrors, along with optical metrology slope profiles demonstrating their exceptionally high quality. This work provides a systematic and comprehensive study of the accuracy provided by curved gratings in real-time imaging of X-ray beams at a free-electron laser facility. It is applied here to soft X-rays and can be extended to the hard X-ray range. Furthermore, curved gratings, in combination with a suitable detector, can provide spatial properties of µm-focused X-ray beams at MHz repetition rate.
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May 2022
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Metrology
Optics
|
Giuseppe
Mercurio
,
Carsten
Broers
,
Robert
Carley
,
Jan Torben
Delitz
,
Natalia
Gerasimova
,
Loïc
Le Guyarder
,
Laurent
Mercadier
,
Alexander
Reich
,
Justine
Schlappa
,
Martin
Teichmann
,
Alexander
Yaroslavtsev
,
Michele
Cascella
,
Kiana
Setoodehnia
,
Michael
Schneider
,
Bastian
Pfau
,
Stefan
Eisebitt
,
Vojtech
Vozda
,
Anna
Hajkova
,
Ludek
Vysin
,
Tomas
Burian
,
Jaromir
Chalupský
,
Libor
Juha
,
Simon G.
Alcock
,
Ioana-Theodora
Nistea
,
Daniele
La Civita
,
Harald
Sinn
,
Maurizio
Vannoni
,
Andreas
Scherz
Abstract: The Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL is a soft X-ray beamline aiming to unravel electronic, spin and structural properties of materials in ultrafast processes at the nanoscale. Various experimental techniques offered at SCS have different requirements in terms of beam size at the sample. Kirkpatrick-Baez (KB) refocusing optics equipped with mechanical benders allows for independent change of the horizontal and vertical beam size. We report here on the first characterization of the SCS KB mirrors by means of a novel diffraction-based technique which images the beam profile on a 2D pixelated detector. This approach provides a quick characterization of micrometer beam sizes. Results are compared with metrology measurements obtained with a non-contact slope profiler.
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Sep 2019
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I09-Surface and Interface Structural Analysis
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Open Access
Abstract: We introduce a software, Torricelli, for the analysis of normal incidence x-ray standing wave data. In particular, given the experimental x-ray reflectivity and photoelectron yield of a data set (photon energy scan), Torricelli provides the corresponding structural parameters. The algorithm and equations on which Torricelli is based are explained here in detail. In particular, the model of the experimental reflectivity takes into account the theoretical reflectivity of the double crystal monochromator as well as the sample crystal, and a Gaussian broadening to account for mosaicity and photon energy spread. If statistical errors are provided together with the photoelectron yield data, these are propagated to produce the statistical errors of the structural parameters. For a more accurate analysis, angle-dependent correction parameters specific to the photoemission process, also beyond the dipole approximation, can be taken into account, especially in the case of non-perfect normal incidence. The obtained structural parameters can be compared, averaged, and displayed in an Argand diagram, along with statistical error bars.
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Dec 2018
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