A5032688391- Ferroelectric and Piezoelectric Materials
- Multiferroics and related materials
- Radiation Detection and Scintillator Technologies
- Atomic and Subatomic Physics Research
- Magnetic and transport properties of perovskites and related materials
- Luminescence Properties of Advanced Materials
- Electronic and Structural Properties of Oxides
- Chalcogenide Semiconductor Thin Films
- Semiconductor materials and interfaces
- Solidification and crystal growth phenomena
- Nuclear Physics and Applications
- Advanced Semiconductor Detectors and Materials
- Semiconductor Quantum Structures and Devices
- X-ray Diffraction in Crystallography
- Acoustic Wave Resonator Technologies
- Crystallization and Solubility Studies
- Quantum Dots Synthesis And Properties
- Silicon and Solar Cell Technologies
- nanoparticles nucleation surface interactions
- Dielectric properties of ceramics
- Solid-state spectroscopy and crystallography
- Semiconductor materials and devices
- Ion-surface interactions and analysis
- Medical Imaging Techniques and Applications
- Dark Matter and Cosmic Phenomena
Lawrence Berkeley National Laboratory
2015-2024
University of California, Berkeley
1987-2021
Norwegian University of Science and Technology
2020-2021
University of Augsburg
2021
Berkeley College
2020
University of California, Davis
2020
ETH Zurich
2020
Cyclotron (Netherlands)
2020
Cranfield University
2018
Twin Cities Orthopedics
2017
Abstract New developments in liquid scintillators, high-efficiency, fast photon detectors, and chromatic sorting have opened up the possibility for building a large-scale detector that can discriminate between Cherenkov scintillation signals. Such could reconstruct particle direction species using light while also having excellent energy resolution low threshold of scintillator detector. Situated deep underground, utilizing new techniques computing reconstruction, this achieve unprecedented...
Diverse topological defects arise in hexagonal manganites, such as ferroelectric vortices, well neutral and charged domain walls. The are intriguing because their low symmetry enables unusual couplings between structural, charge, spin degrees of freedom, holding great potential for novel types functional 2D 1D systems. Despite the considerable advances analyzing different understanding key intrinsic properties is still rather limited disconnected. In particular, a rapidly increasing number...
The emergence of long-range magnetic order in noncentrosymmetric compounds has stimulated interest the possibility exotic spin transport phenomena and topologically protected textures for applications next-generation spintronics. Polar magnets, with broken symmetries spatial inversion time reversal, usually host chiral textures. This work reports on a wurtzite-structure polar metal, identified as AA′-stacked (Fe0.5Co0.5)5GeTe2, which exhibits Néel-type skyrmion lattice well Rashba-Edelstein...
A key to the unique combination of electronic and optical properties in halide perovskite materials lies their rich structural complexity. However, radiation sensitive nature limits nanoscale characterization requiring dose efficient microscopic techniques order determine structures precisely. In this work, we space-group directly image Br sites CsPbBr3, a promising material for optoelectronic applications. Based on symmetry high-order Laue zone reflections convergent-beam electron...
Layered oxides exhibit high ionic mobility and chemical flexibility, attracting interest as cathode materials for lithium-ion batteries the pairing of hydrogen production carbon capture. Recently, layered emerged highly tunable semiconductors. For example, by introducing anti-Frenkel defects, electronic hopping conductance in hexagonal manganites was increased locally orders magnitude. Here, we demonstrate local acceptor donor doping Er(Mn,Ti)O$_3$, facilitated splitting such defects under...
The Kibble-Zurek mechanism describes the formation of topological defects in wake continuous phase transitions. A new analysis presents a global upgrade to this picture that reveals phenomena as fluctuations system transform from strongly interacting noninteracting.
A combinatorial approach where doped bulk scintillator materials can be rapidly optimized for their properties through concurrent extrinsic doping/co-doping strategies is presented. The concept that makes use of design experiment, rapid growth, and evaluation techniques, multivariable regression analysis, has been successfully applied to the engineering NaI performance, a historical but mediocre performer in scintillation detection. Using this approach, we identified three-element strategy...
Acceptor and donor doping is a standard for tailoring semiconductors. More recently, was adapted to optimize the behavior at ferroelectric domain walls. In contrast more than century of research on semiconductors, impact chemical substitutions local electronic response walls largely unexplored. Here, hexagonal manganite ${\mathrm{ErMnO}}_{3}$ doped with ${\mathrm{Ti}}^{4+}$. Density functional theory calculations show that ${\mathrm{Ti}}^{4+}$ goes $B$ site, replacing ${\mathrm{Mn}}^{3+}$....
Engineering of ferroelectric domain structures enables direct control over the switching dynamics and is crucial for tuning functional properties ferroelectrics various applications, ranging from capacitors to future nanoelectronics. Here, we investigate formation in poly- single-crystalline improper hexagonal DyMnO3. We show that a non-uniform grain-size distribution polycrystal facilitates coexistence multi-scale domains, varying by up one order magnitude size. This unusual structure...
Electronic domain-wall conductance is controlled by chemical aliovalent doping in the p-type semiconductor Er1-xCaxMnO3. Coexisting bound (top panel) and mobile (lower charges at walls are analyzed using electrostatic force microscopy. Emergent doping-related variations quantified local transport measurements explained based on phenomenological theories.
Low-temperature electrostatic force microscopy (EFM) is used to probe unconventional domain walls in the improper ferroelectric semiconductor Er0.99Ca0.01MnO3 down cryogenic temperatures. The low-temperature EFM maps reveal pronounced electric far fields generated by partially uncompensated domain-wall bound charges. Positively and negatively charged display qualitatively different as a function of temperature, which we explain based on screening mechanisms corresponding relaxation time...
We report an electric-field poling study of the geometrically-driven improper ferroelectric h-ErMnO3. From a detailed dielectric analysis, we deduce temperature and frequency dependent range for which single-crystalline h-ErMnO3 exhibits purely intrinsic behaviour, i.e., free from extrinsic so-called Maxwell-Wagner polarisations that arise, example, surface barrier layers. In this regime, hysteresis loops as function frequency, temperature, applied electric fields are measured, revealing...
Ferroelectric domain walls are quasi-2D systems that show great promise for the development of nonvolatile memory, memristor technology, and electronic components with ultrasmall feature size. Electric fields, example, can change wall orientation relative to spontaneous polarization switch between resistive conductive states, controlling electrical current. Being embedded in a 3D material, however, not perfectly flat form networks, which leads complex physical structures. In this work,...
Abstract Extraordinary physical properties arise at polar interfaces in oxide materials, including the emergence of 2D electron gases, sheet‐superconductivity, and multiferroicity. A special type interface is ferroelectric domain walls, where electronic reconstruction phenomena can be driven by bound charges. Great progress has been achieved characterization such walls and, over last decade, their potential for next‐generation nanotechnology become clear. Established tomography techniques,...
We investigate the effect of chemical doping on electric and magnetic domain pattern in multiferroic hexagonal ErMnO3. Hole- electron are achieved through growth Er1−xCaxMnO3 Er1−xZrxMnO3 single crystals, which allows for a controlled introduction divalent tetravalent ions, respectively. Using conductance measurements, piezoresponse force microscopy nonlinear optics we study doping-related variations electronic transport image corrsponding ferroelectric antiferromagnetic domains. find that...
High-resolution X-ray photoemission electron microscopy (X-PEEM) is a well-established method for imaging ferroelectric domain structures. Here, we expand the scope of application X-PEEM and demonstrate its capability investigating walls in ferroelectrics with high-spatial resolution. Using ErMnO3 as test system, show that can be visualized based on photo-induced charging effects local variations their electronic conductance mapped by analyzing energy distribution photoelectrons. Our results...
Direct measurements of the critical resolved shear stress undoped and indium-doped GaAs single crystals at high temperatures have been performed using dynamical compression tests. At melting point GaAs:In is only twice that GaAs. low temperatures, activation energy for motion dislocations not affected by indium doping. From these findings we conclude crystallographic glide cause dislocation formation in solution hardening responsible reduction density GaAs:In.