I09-Surface and Interface Structural Analysis
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Jieyi
Liu
,
Yiheng
Yang
,
Jianlei
Shen
,
Defa
Liu
,
Gohil Singh
Thakur
,
Charles
Guillemard
,
Alevtina
Smekhova
,
Houke
Chen
,
Deepnarayan
Biswas
,
Manuel
Valvidares
,
Enke
Liu
,
Claudia
Felser
,
Tien-Lin
Lee
,
Thorsten
Hesjedal
,
Yulin
Chen
,
Gerrit
Van Der Laan
Diamond Proposal Number(s):
[37930]
Open Access
Abstract: The physical properties of magnetic topological materials are strongly influenced by their nontrivial band topology coupled with the magnetic structure. Co3Sn2S2 is a ferromagnetic kagome Weyl semimetal displaying giant intrinsic anomalous Hall effect which can be further tuned via elemental doping, such as Ni substitution for Co. Despite significant interest, the exact valency of Co and the magnetic order of the Ni dopants remained unclear. Here, we report a study of Ni-doped Co3Sn2S2 single crystals using synchrotron-based X-ray magnetic circular dichroism (XMCD), X-ray photoelectron emission microscopy (XPEEM), and hard/soft X-ray photoemission spectroscopy (XPS) techniques. We confirm the presence of spin-dominated magnetism from Co in the host material, and also the establishment of ferromagnetic order from the Ni dopant. The oxygen-free photoemission spectrum of the Co 2p core levels in the crystal well resembles that of a metallic Co film, indicating a Co0+ valency. Surprisingly, we find the electron filling in the Co 3d state can reach 8.7–9.0 electrons in these single crystals. Our results highlight the importance of element-specific X-ray spectroscopy in understanding the electronic and magnetic properties that are fundamental to a heavily studied Weyl semimetal, which could aid in developing future spintronic applications based on magnetic topological materials.
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Feb 2025
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[33305, 33757]
Open Access
Abstract: On-surface synthesis of functional molecular structures provides a route to the fabrication of materials tailored to exhibit bespoke catalytic, (opto)electronic, and magnetic properties. The fabrication of graphene nanoribbons via on-surface synthesis, where reactive precursor molecules are combined to form extended polymeric structures, provides quasi-1D graphitic wires that can be doped by tuning the properties/composition of the precursor molecules. Here, we combine the atomic precision of solution-phase synthetic chemistry with on-surface protocols to enable reaction steps that cannot yet be achieved in solution. Our focus of this work is the inclusion of porphyrin species within graphene nanoribbons to create porphyrin-fused graphene nanoribbons. A combination of scanning tunneling microscopy and photoelectron spectroscopy techniques is used to characterize a porphyrin-fused graphene nanoribbon formed on-surface from a linear polymer consisting of regularly spaced Ni-porphyrin units linked by sections of aryl rings which fuse together during the reaction to form graphitic regions between neighboring Ni-porphyrin units.
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Nov 2024
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I05-ARPES
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Diamond Proposal Number(s):
[26631]
Open Access
Abstract: Interaction between electrons and phonons in solids is a key effect defining the physical properties of materials, such as electrical and thermal conductivity. In transition metal dichalcogenides (TMDCs), the electron–phonon coupling results in the formation of polarons, quasiparticles that manifest themselves as discrete features in the electronic spectral function. In this study, we report the formation of polarons at the alkali-dosed MoSe2 surface, where Rashba-like spin splitting of the conduction band states is caused by an inversion-symmetry breaking electric field. In addition, we observed a crossover from phonon-like to plasmon-like polaronic spectral features at the MoSe2 surface with increasing doping. Our findings support the concept of electron–phonon coupling-mediated superconductivity in electron-doped layered TMDC materials, as observed using ionic liquid gating technology. Furthermore, the discovered spin-splitting at the Fermi level could offer crucial experimental validation for theoretical models of Ising-type superconductivity in these materials.
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Nov 2024
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I22-Small angle scattering & Diffraction
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Kenza
Djeghdi
,
Dmitry
Karpov
,
S. Narjes
Abdollahi
,
Karolina
Godlewska
,
René
Iseli
,
Mirko
Holler
,
Claire
Donnelly
,
Takeshi
Yuasa
,
Hiroaki
Sai
,
Ulrich B.
Wiesner
,
Ullrich
Steiner
,
Bodo D.
Wilts
,
Michimasa
Musya
,
Shunsuke
Fukami
,
Hideo
Ohno
,
Ana
Diaz
,
Justin
Llandro
,
Ilja
Gunkel
Diamond Proposal Number(s):
[18392]
Open Access
Abstract: Block copolymers are recognized as a valuable platform for creating nanostructured materials. Morphologies formed by block copolymer self-assembly can be transferred into a wide range of inorganic materials, enabling applications including energy storage and metamaterials. However, imaging of the underlying, often complex, nanostructures in large volumes has remained a challenge, limiting progress in materials development. Taking advantage of recent advances in X-ray nanotomography, we noninvasively imaged exceptionally large volumes of nanostructured hybrid materials at high resolution, revealing a single-diamond morphology in a triblock terpolymer–gold composite network. This morphology, which is ubiquitous in nature, has so far remained elusive in block copolymer-derived materials, despite its potential to create materials with large photonic bandgaps. The discovery was made possible by the precise analysis of distortions in a large volume of the self-assembled diamond network, which are difficult to unambiguously assess using traditional characterization tools. We anticipate that high-resolution X-ray nanotomography, which allows imaging of much larger sample volumes than electron-based tomography, will become a powerful tool for the quantitative analysis of complex nanostructures and that structures such as the triblock terpolymer-directed single diamond will enable the generation of advanced multicomponent composites with hitherto unknown property profiles.
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Sep 2024
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I13-1-Coherence
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Diamond Proposal Number(s):
[33421]
Abstract: Promotion of oxygen reduction reaction (ORR) kinetics, to a large extent, depends on the rational modulation of the electronic structure and mass diffusion of electrocatalysts. Herein, a ferrocene (Fc)–assisted strategy is developed to prepare Fc-trapped ZnMo–hybrid zeolitic imidazolate framework (Fc@ZnMo-HZIF-50) and the derived Fe single atom coupling with MoC nanoparticles, coembedded in hierarchically porous N-doped carbon cubes (MoC@FeNC-50). The introduced Fc is utilized not only as an iron source for single atoms but also as a morphology regulator for generating a hierarchically porous structure. The redistribution of electrons between Fe single atoms and MoC nanoparticles effectively promotes the adsorption of O2 and the formation of *OOH intermediates during the ORR process. Along with a 3D hierarchically porous architecture for enhanced mass transport, the as-fabricated MoC@FeNC-50 presents excellent activity (E1/2 = 0.83 V) and durability (only 9.5% decay in current after 40000 s). This work could inspire valuable insights into the construction of efficient electrocatalysts through electron configuration and kinetics engineering.
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Aug 2024
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[32019]
Open Access
Abstract: Lead chalcogenide colloidal quantum dots are one of the most promising materials to revolutionize the field of short-wavelength infrared optoelectronics due to their bandgap tunability and strong absorption. By self-assembling these quantum dots into ordered superlattices, mobilities approaching those of the bulk counterparts can be achieved while still retaining their original optical properties. The recent literature focused mostly on PbSe-based superlattices, but PbS quantum dots have several advantages, including higher stability. In this work, we demonstrate highly ordered 3D superlattices of PbS quantum dots with tunable thickness up to 200 nm and high coherent ordering, both in-plane and along the thickness. We show that we can successfully exchange the ligands throughout the film without compromising the ordering. The superlattices as the active material of an ion gel-gated field-effect transistor achieve electron mobilities up to 220 cm2 V–1 s–1. To further improve the device performance, we performed a postdeposition passivation with PbI2, which noticeably reduced the subthreshold swing making it reach the Boltzmann limit. We believe this is an important proof of concept showing that it is possible to overcome the problem of high trap densities in quantum dot superlattices enabling their application in optoelectronic devices.
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Jul 2024
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Zhou
Shen
,
Paul Lourdu
Xavier
,
Richard
Bean
,
Johan
Bielecki
,
Martin
Bergemann
,
Benedikt
Daurer
,
Tomas
Ekeberg
,
Armando D.
Estillore
,
Hans
Fangohr
,
Klaus
Giewekemeyer
,
Mikhail
Karnevskiy
,
Richard A.
Kirian
,
Henry
Kirkwood
,
Yoonhee
Kim
,
Jayanath C. P.
Koliyadu
,
Holger
Lange
,
Romain
Letrun
,
Jannik
Lübke
,
Abhishek
Mall
,
Thomas
Michelat
,
Andrew J.
Morgan
,
Nils
Roth
,
Amit K.
Samanta
,
Tokushi
Sato
,
Marcin
Sikorski
,
Florian
Schulz
,
Patrik
Vagovic
,
Tamme
Wollweber
,
Lena
Worbs
,
Filipe
Maia
,
Daniel A.
Horke
,
Jochen
Küpper
,
Adrian P.
Mancuso
,
Henry
Chapman
,
Kartik
Ayyer
,
N. Duane
Loh
Open Access
Abstract: Nanoparticles, exhibiting functionally relevant structural heterogeneity, are at the forefront of cutting-edge research. Now, high-throughput single-particle imaging (SPI) with X-ray free-electron lasers (XFELs) creates opportunities for recovering the shape distributions of millions of particles that exhibit functionally relevant structural heterogeneity. To realize this potential, three challenges have to be overcome: (1) simultaneous parametrization of structural variability in real and reciprocal spaces; (2) efficiently inferring the latent parameters of each SPI measurement; (3) scaling up comparisons between 105 structural models and 106 XFEL-SPI measurements. Here, we describe how we overcame these three challenges to resolve the nonequilibrium shape distributions within millions of gold nanoparticles imaged at the European XFEL. These shape distributions allowed us to quantify the degree of asymmetry in these particles, discover a relatively stable “shape envelope” among nanoparticles, discern finite-size effects related to shape-controlling surfactants, and extrapolate nanoparticles’ shapes to their idealized thermodynamic limit. Ultimately, these demonstrations show that XFEL SPI can help transform nanoparticle shape characterization from anecdotally interesting to statistically meaningful.
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May 2024
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I14-Hard X-ray Nanoprobe
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Diamond Proposal Number(s):
[22232]
Open Access
Abstract: Erucamide is known to play a critical role in modifying polymer fiber surface chemistry and morphology. However, its effects on fiber crystallinity and mechanical properties remain to be understood. Here, synchrotron nanofocused X-ray Diffraction (nXRD) revealed a bimodal orientation of the constituent polymer chains aligned along the fiber axis and cross-section, respectively. Erucamide promoted crystallinity in the fiber, leading to larger and more numerous lamellae crystallites. The nXRD nanostructual characterization is complemented by single-fiber uniaxial tensile tests, which showed that erucamide significantly affected fiber mechanical properties, decreasing fiber tensile strength and stiffness but enhancing fiber toughness, fracture strain, and ductility. To correlate these single-fiber nXRD and mechanical test results, we propose that erucamide mediated slip at the interfaces between crystallites and amorphous domains during stress-induced single-fiber crystallization, also decreasing the stress arising from the shear displacement of microfibrils and deformation of the macromolecular network. Linking the single-fiber crystal structure with the single-fiber mechanical properties, these findings provide the direct evidence on a single-fiber level for the role of erucamide in enhancing fiber “softness”.
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Feb 2024
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E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[20345]
Abstract: Moiré superlattices in graphene arise from rotational twists in stacked 2D layers, leading to specific band structures, charge density and interlayer electron and excitonic interactions. The periodicities in bilayer graphene moiré lattices are given by a simple moiré basis vector that describes periodic oscillations in atomic density. The addition of a third layer to form trilayer graphene generates a moiré lattice comprised of multiple harmonics that do not occur in bilayer systems, leading to nontrivial crystal symmetries. Here, we use atomic resolution 4D-scanning transmission electron microscopy to study atomic structure in bilayer and trilayer graphene moiré superlattices and use 4D-STEM to map the electric fields to show subtle variations in the long-range moiré patterns. We show that monolayer graphene folded into an S-bend graphene pleat produces trilayer moiré superlattices with both small (<2°) and larger twist angles (7–30°). Annular in-plane electric field concentrations are detected in high angle bilayers due to overlapping rotated graphene hexagons in each layer. The presence of a third low angle twisted layer in S-bend trilayer graphene, introduces a long-range modulation of the atomic structure so that no real space unit cell is detected. By directly imaging trilayer moiré harmonics that span from picoscale to nanoscale using 4D-STEM, we gain insights into the complex spatial distributions of atomic density and electric fields in trilayer twisted layered materials.
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Oct 2023
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I18-Microfocus Spectroscopy
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Lydia
Martínez-Parra
,
Marina
Piñol-Cancer
,
Carlos
Sanchez-Cano
,
Ana B.
Miguel-Coello
,
Desirè
Di Silvio
,
Ana M.
Gomez
,
Clara
Uriel
,
Sandra
Plaza-García
,
Marta
Gallego
,
Raquel
Pazos
,
Hugo
Groult
,
Marc
Jeannin
,
Kalotina
Geraki
,
Laura
Fernández-Méndez
,
Ainhize
Urkola-Arsuaga
,
María Jesús
Sánchez-Guisado
,
Juliana
Carrillo-Romero
,
Wolfgang J.
Parak
,
Maurizio
Prato
,
Fernando
Herranz
,
Jesus
Ruiz-Cabello
,
Susana
Carregal-Romero
Diamond Proposal Number(s):
[27720]
Open Access
Abstract: Atherosclerosis is a complex disease that can lead to life-threatening events, such as myocardial infarction and ischemic stroke. Despite the severity of this disease, diagnosing plaque vulnerability remains challenging due to the lack of effective diagnostic tools. Conventional diagnostic protocols lack specificity and fail to predict the type of atherosclerotic lesion and the risk of plaque rupture. To address this issue, technologies are emerging, such as noninvasive medical imaging of atherosclerotic plaque with customized nanotechnological solutions. Modulating the biological interactions and contrast of nanoparticles in various imaging techniques, including magnetic resonance imaging, is possible through the careful design of their physicochemical properties. However, few examples of comparative studies between nanoparticles targeting different hallmarks of atherosclerosis exist to provide information about the plaque development stage. Our work demonstrates that Gd (III)-doped amorphous calcium carbonate nanoparticles are an effective tool for these comparative studies due to their high magnetic resonance contrast and physicochemical properties. In an animal model of atherosclerosis, we compare the imaging performance of three types of nanoparticles: bare amorphous calcium carbonate and those functionalized with the ligands alendronate (for microcalcification targeting) and trimannose (for inflammation targeting). Our study provides useful insights into ligand-mediated targeted imaging of atherosclerosis through a combination of in vivo imaging, ex vivo tissue analysis, and in vitro targeting experiments.
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Jul 2023
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