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Uniaxial strain-driven ferroelastic domain control in LaAlO3
Authors:
Matthias Roeper,
Robin Buschbeck,
Jakob Wetzel,
Tobias Ritschel,
Anna-Lena Hofmann,
Vladyslav Kovtunovych,
Mike N. Pionteck,
Javier Taboada-Gutiérrez,
Alexey B. Kuzmenko,
Martina Basini,
Vivek Unikandanunni,
Iuliia Kiseleva,
Jochen Geck,
Susanne C. Kehr,
Maximilian Lederer,
Simone Sanna,
Lukas M. Eng,
Samuel D. Seddon
Abstract:
Multiferroic domain walls in functional oxides exhibit properties distinct from the bulk and are increasingly exploited as active elements in nanoelectronic and photonic devices. Deterministic control of domain populations has typically remained limited to local control, or removal with temperature. Here we demonstrate continuous, reversible manipulation of the ferroelastic domain structure in sin…
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Multiferroic domain walls in functional oxides exhibit properties distinct from the bulk and are increasingly exploited as active elements in nanoelectronic and photonic devices. Deterministic control of domain populations has typically remained limited to local control, or removal with temperature. Here we demonstrate continuous, reversible manipulation of the ferroelastic domain structure in single-crystal LaAlO$_3$ using in-situ uniaxial strain. Combining atomic force microscopy, X-ray diffraction, and Raman spectroscopy with first-principles calculations we map the complete microscopic evolution of the twin domain population through the strain-driven transition from the rhombohedral $R\bar{3}c$ ground state toward the predicted orthorhombic $Fmmm$ phase. Applied strains below $0.5\%$ produce pronounced surface flattening and large-scale domain reorganisation, establishing uniaxial strain as a technically accessible control parameter for ferroelastic domain engineering. These results open a route to active, real-time programming of domain architectures in LaAlO$_3$-based heterostructures, with implications for strain-tunable superconducting interfaces, nanoscale phonon-polariton optics, and ultrafast lattice control.
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Submitted 30 April, 2026;
originally announced April 2026.
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Enhanced Performance of FeFET Gate Stack via Heterogeneously co-doped Ferroelectric HfO$_2$ Films
Authors:
Shouzhuo Yang,
David Lehninger,
Peter Reinig,
Fred Schöne,
Raik Hoffmann,
Konrad Seidel,
Maximilian Lederer,
Gerald Gerlach
Abstract:
In this work, we explore the impact of spatially controlled Zr and Al heterogeneous co-doping in HfO$_2$ thin films tailored for metal-ferroelectric-insulator-semiconductor (MFIS) gate stacks of ferroelectric field effect transistors (FeFETs). By precisely modulating the vertical arrangement of Zr and Al dopants during atomic layer deposition, we introduce deliberate compositional gradients that a…
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In this work, we explore the impact of spatially controlled Zr and Al heterogeneous co-doping in HfO$_2$ thin films tailored for metal-ferroelectric-insulator-semiconductor (MFIS) gate stacks of ferroelectric field effect transistors (FeFETs). By precisely modulating the vertical arrangement of Zr and Al dopants during atomic layer deposition, we introduce deliberate compositional gradients that affect crystallization dynamics during subsequent annealing. This strategy enables us to systematically tune the phase evolution and domain nucleation within the ferroelectric layer, directly influencing device reliability and performance. From a structural perspective, our findings demonstrate that the phase composition of annealed HfO$_2$ films in MFIS stacks is primarily determined by the spatial arrangement of dopants. From an electrical perspective, we observe significant enhancement of remanent polarization and endurance of the gate stacks through heterogeneous co-doping, depending on the spatial arrangement of dopants.
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Submitted 22 August, 2025;
originally announced August 2025.
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Revealing the Influence of Dopants on the Properties of Fluorite Structure Ferroelectrics
Authors:
Shouzhuo Yang,
David Lehninger,
Markus Neuber,
Amir Pourjafar,
Ayse Sünbül,
Anant Rastogi,
Peter Reinig,
Konrad Seidel,
Maximilian Lederer
Abstract:
Fluorite structure ferroelectrics, especially hafnium oxide, are widely investigated for their application in non-volatile memories, sensors, actuators, RF devices and energy harvesters. Due to the metastable nature of the ferroelectric phase in these materials, dopants and process parameters need to be optimized for its stabilization. Here, we present clear evidence of how dopants affect the prop…
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Fluorite structure ferroelectrics, especially hafnium oxide, are widely investigated for their application in non-volatile memories, sensors, actuators, RF devices and energy harvesters. Due to the metastable nature of the ferroelectric phase in these materials, dopants and process parameters need to be optimized for its stabilization. Here, we present clear evidence of how dopants affect the properties in this material system and solutions to achieve improved reliability, desired crystallization behavior and polarization hysteresis shape/position through co-doping. Finally, the benefits of co-doping in a variety of application fields are demonstrated.
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Submitted 22 August, 2025;
originally announced August 2025.
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Megahertz-rate Ultrafast X-ray Scattering and Holographic Imaging at the European XFEL
Authors:
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,
Igor Pronin,
Marina Baidakova,
Clemens von Korff Schmising,
Martin Borchert
, et al. (75 additional authors not shown)
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, we presen…
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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, we present the results from the first megahertz repetition rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL. We illustrate the experimental capabilities that the SCS instrument offers, resulting from the operation at MHz repetition rates and the availability of the novel DSSC 2D imaging detector. 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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Submitted 20 January, 2022; v1 submitted 17 January, 2022;
originally announced January 2022.
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Incorporation and control of defects with quantum functionality during sublimation growth of cubic silicon carbide
Authors:
Michael Schöler,
Maximilian W. Lederer,
Philipp Schuh,
Peter J. Wellmann
Abstract:
Superconductor based quantum computing has the major drawback of working temperatures which require liquid helium for cooling. A promising approach to overcome this obstacle for quantum technologies is based on deep level defects in semiconductors, with the nitrogen vacancy (NV) center in diamond being the most prominent example. Unfortunately, diamond in sufficient quality is scarce, which motiva…
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Superconductor based quantum computing has the major drawback of working temperatures which require liquid helium for cooling. A promising approach to overcome this obstacle for quantum technologies is based on deep level defects in semiconductors, with the nitrogen vacancy (NV) center in diamond being the most prominent example. Unfortunately, diamond in sufficient quality is scarce, which motivated efforts to find similar defects in silicon carbide (SiC). So far, many reports focus on investigations of point defects in irradiated 3C-SiC and as grown material. However, the investigated defects are more or less a product of coincidence for both. While in irradiated material the intentional generation of specific defects is rather challenging, in as purchased material the defects are actually more an unintentional by product of growth and process conditions. This work proposes a new route: the incorporation and control of deep level defects in 3C-SiC by epitaxial sublimation growth. The observed defects in the near infrared show bright luminescence in the 175 K/200 K regime and remain excitable up to 300 K. This could enable working temperatures above the cryogenic limit. The joint origin of all detected defects is assigned to the carbon vacancy.
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Submitted 18 June, 2019;
originally announced June 2019.