Optics
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Arindam
Majhi
,
Wadwan
Singhapong
,
Wai Jue
Tan
,
Andrey
Sokolov
,
Stefano
Agrestini
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Andrew C.
Walters
,
Chris
Bowen
,
Alexander J. G.
Lunt
,
Hongchang
Wang
,
Kawal J.
Sawhney
Open Access
Abstract: Laterally graded multilayer optics play an important role in advanced X-ray applications, enabling precise control of beam properties for spectroscopic and focusing techniques. The Multilayer Deposition System (MDS) at Diamond Light Source (DLS) has demonstrated its ability to fabricate highly precise laterally graded X-ray optics. Developing such optics is challenging due to stringent requirements for precise lateral thickness variations and sagittal uniformity, achieved through optimized substrate speed profiles and advanced mask design. This study presents a comprehensive investigation into the design, fabrication, and characterization of laterally graded multilayers. An adjustable mask design improves sagittal uniformity and reduces optimization times. The structural and optical performance of the multilayers is evaluated, confirming their suitability for synchrotron applications. Two types of laterally graded multilayers were developed: one with a constant lateral gradient (0.005 nm/mm) for O-K edge polarizers, achieving sagittal thickness variations of approximately 0.3–0.4% across an 80 mm substrate, and another featuring a strong variable gradient from 0.037 to 0.112 nm/mm, designed to match the elliptical periodicity profile. The constant gradient multilayer polarizer has been successfully implemented on the state-of-the-art I21 beamline at DLS, highlighting the MDS's role in producing next-generation X-ray optics that meet the stringent demands of synchrotron beamlines.
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Jan 2026
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I05-ARPES
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Shu
Mo
,
Ksenija
Kovalenka
,
Sebastian
Buchberger
,
Bruno K.
Saika
,
Anugrah
Azhar
,
Akhil
Rajan
,
Andela
Zivanovic
,
Yu-Chi
Yao
,
Rodion V.
Belosludov
,
Matthew D.
Watson
,
M. Saeed
Bahramy
,
Phil D. C.
King
Diamond Proposal Number(s):
[36192]
Open Access
Abstract: Moiré heterostructures, created by stacking 2D materials together with a finite lattice mismatch or rotational twist, represent a new frontier of designer quantum materials. Typically, however, this requires the painstaking manual assembly of heterostructures formed from exfoliated materials. Here, clear spectroscopic signatures of moiré lattice formation in epitaxial heterostructures of monolayer (ML) NbSe2 grown on graphite substrates are observed. Angle-resolved photoemission measurements and theoretical calculations of the resulting electronic structure reveal moiré replicas of the graphite π states forming pairs of interlocking Dirac cones. Interestingly, these intersect the NbSe2 Fermi surface at the -space locations where NbSe2's charge-density wave (CDW) gap is maximal in the bulk. This provides a natural route to understand the lack of CDW enhancement for ML-NbSe2/graphene as compared to a more than fourfold enhancement for NbSe2 on insulating support substrates, and opens new prospects for using moiré engineering for controlling the collective states of 2D materials.
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Dec 2025
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
I15-1-X-ray Pair Distribution Function (XPDF)
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Daniel
Muñoz-Gil
,
Celia
Castillo-Blas
,
Dawid Krystian
Feler
,
Isabel
Gómez-Recio
,
Miguel
Tinoco
,
Ana
Querejeta-Fernández
,
Rodrigo
González-Prieto
,
Felipe
Gandara
,
Romualdo
Santos Silva
,
Pilar
Ferrer
,
Carlos
Prieto
,
Luc
Lajaunie
,
José Luis
Martinez-Peña
,
María Luisa
Ruiz-González
,
María Luisa
Ruiz-González
,
José María
González-Calbet
Diamond Proposal Number(s):
[40307, 40403]
Open Access
Abstract: Layered double hydroxides (LDH) based on transition metals are highly flexible in tailoring their dimensionality, lattice, and electronic structures, making them promising candidates as multifunctional 2D materials for the development of clean energy technologies and boosting the use of hydrogen as an energy vector. In this paper, strategic anion substitution in cobalt LDH is an appealing strategy to produce a material with two-fold functionality, electrochemical and magnetocaloric response, offering a sustainable alternative to existing electrocatalysts and cryogenic refrigerants. It is unambiguously demonstrated that (poly)oxomolybdate-based specimens interleave in Co LDH nanosheets up to a Co:Mo = 1:0.4 ratio, leading to an interstratified material. This intercalation greatly benefits the kinetics of the oxygen evolution reaction for H2 production, boosting the catalytic sites due to the expansion of the interlayer space, induced by the bulky molybdates which also partially modify the Co oxidation state of αCo(OH)2 nanolayers, favoring charge transfer. In parallel, the interleaved Mo species strengthen superexchange interactions compared with pristine α-Co(OH)2, effectively adjusting the operating temperature toward the liquid hydrogen range (2030 K). This specific temperature range allows to fill a critical gap in magnetocaloric materials, as few systems can simultaneously achieve both large magnetic entropy changes and structural stability.
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Oct 2025
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Yafei
Chu
,
Chaocheng
Liu
,
Ruiqi
Liu
,
Weican
Lan
,
Lu
Cheng
,
Huijuan
Wang
,
Minghui
Fan
,
Hengli
Duan
,
Chao
Wang
,
Yajuan
Feng
,
Wensheng
Yan
Abstract: Twisted bilayer transition metal dichalcogenides (TMDs) have generated diverse unusual electrical and optical phenomena and can provide a powerful platform for designing nanodevices with tunable interlayer interaction. Striving to explore novel excitons with spin response in these semiconductor systems is highly desirable, as they highlight the possibility to access complex electronic band structure and magneto-exciton effect, thereby facilitating efficient spin-based information storage via exciton degrees of freedom. Here, fabrication of bilayer WSe2/Fe5GeTe2 (FGT) heterostructures with different stacking phases is reported, and a new hybridized excitonic state T* is defined in both 3R and 2H bilayer WSe2, which exhibits strong correlations dependent on the FGT spin order. This spin-dependent hybridized exciton is demonstrated to originate from the coupling between injected spin-polarized electrons and neutral excitons, because of the spin-cross-polarized band that obstructs the normal electron–hole annihilation process. Besides, the difference in the coupling strength of the T* exciton attributed to the distinct stacking symmetries in twisted bilayer WSe2 is further unveiled. These findings open an accessible avenue for designing tailored excitonic states in twisted bilayers, thus offering prospects for the future applications of stacking-engineered opto-spintronics at the integration level.
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Oct 2025
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I05-ARPES
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Qun
Wang
,
Yifang
Jiang
,
Songyuan
Geng
,
Hanpu
Liang
,
Yunbo
Wu
,
Risi
Guo
,
Fangjie
Chen
,
Kangjie
Li
,
Xin
Wang
,
Bin
Cao
,
Keyu
An
,
Shengtao
Cui
,
Zhe
Sun
,
Mao
Ye
,
Zhengtai
Liu
,
Changming
Yue
,
Shiming
Lei
,
Haoxiang
Li
Abstract: Engineering narrow-bandgap semiconductors remains a pivotal challenge for next-generation electronic and energy devices. Charge density wave (CDW) systems offer a promising platform for bandgap engineering. However, most 2D and 3D CDW systems remain metallic despite exhibiting Fermi surface nesting. Here, a doping-dependent metal-insulator transition (MIT) with tunable bandgaps is reported in square-net materials GdSbxTe2-x-δ and a cooperative interaction between CDWs and vacancies that drives the MIT is discovered. Angle-resolved photoemission spectroscopy (ARPES) reveals the MIT in the low Sb-content regime of GdSbxTe2-x-δ, with a maximum energy gap of Δ ≈ 98 meV at x = 0.16, corroborated by electrical transport measurements. Following the MIT, X-ray diffraction reveals a doping-dependent shift of the CDW wavevector toward a commensurate structure with q = 0.25 a*, concurrent with the appearance of Te vacancies in the square-net layers. Density functional theory (DFT) calculations attribute the gap formation to the ordered Te vacancies modulated by the 4×1×1 CDW superstructure, which suppresses the electronic states near the Fermi level. Contrasting with the partial gap scenarios in conventional CDW systems, this synergy between the CDW and the vacancy stabilizes the insulating phase, offering a distinct avenue for narrow bandgap engineering in electronic materials.
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Oct 2025
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E02-JEM ARM 300CF
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Stefan
Heiserer
,
Natalie
Galfe
,
Michael
Loibl
,
Maximilian
Wagner
,
Oliver
Hartwig
,
Simon
Schlosser
,
Silke
Boche
,
William
Thornley
,
Nick
Clark
,
Kangho
Lee
,
Tanja
Stimpel‐lindner
,
Cormac
Ó Coileáin
,
Josef
Kiendl
,
Sarah J.
Haigh
,
George J.
De Coster
,
Georg S.
Duesberg
,
Paul
Seifert
Diamond Proposal Number(s):
[30728]
Open Access
Abstract: 2D layered materials such as PtSe2 are prime candidates for next-generation micro- and nano-electro–mechanical systems (MEMS/NEMS), including piezoresistive sensors. However, due to difficulties in large-scale synthesis and the inherent drawbacks associated with mechanical transfer of 2D material films, scalable NEMS production remains challenging. In this work, we report a fabrication route for free-standing, as-grown 2D material channels of PtSe2 with controlled dimensions, avoiding a mechanical film transfer. The free-standing devices provide a universal platform for strain engineering of 2D materials because tension can be easily controlled by application of a back-contact voltage. Moreover, the piezoresistivity of PtSe2, together with the possibility of wafer-scale synthesis at back-end-of-line compatible growth temperatures, make it ideally suited for scalable incorporation into integrated circuits. Our measurements show that the material properties can be tuned via strain, which offers pathways for classically non-gateable materials in electronic and photonic devices. Finite element simulations of representative free-standing films elucidate the nano–mechanical properties of large-scale-grown, polycrystalline 2D materials under tensile strain and demonstrate the influence of polycrystallinity on the optical and electrical behavior.
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Aug 2025
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I11-High Resolution Powder Diffraction
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Jungwoo
Lim
,
Manel
Sonni
,
Luke M.
Daniels
,
Mounib
Bahri
,
Marco
Zanella
,
Ruiyong
Chen
,
Zhao
Li
,
Alex R.
Neale
,
Hongjun
Niu
,
Nigel D.
Browning
,
Matthew S.
Dyer
,
John B.
Claridge
,
Laurence J.
Hardwick
,
Matthew J.
Rosseinsky
Diamond Proposal Number(s):
[31578]
Open Access
Abstract: LiNiO2 positive electrode materials for lithium-ion batteries have experienced a revival of interest due to increasing technological energy demands. Herein a specific Ti4+ substitution is targeted into LiNiO2 to access new compositions by synthesizing the LiNi1–xTi3x/4O2 solid solution with the aim of retaining Ni3+. Compositions in the range 0.025 ≤ x ≤ 0.2 form nanocomposites of compositionally homogeneous ordered R
m and disordered Fm
m rock salt domains as observed via X-ray and neutron diffraction, and STEM. The disordered rock salt domains stabilize the ordered structure to provide excellent structural reversibility via the formation of coherent interfaces during cycling and enable deep delithiation using a constant voltage charging step without structural degradation. The detrimental structural phase transitions associated with the poor cyclability of LiNiO2 are suppressed to yield a low strain positive electrode material with high capacity retention that offers high-rate capability even under increased cell electrode mass loadings. The composition x = 0.075 (LiNi0.925Ti0.05625O2) affords a 93% capacity retention after 100 cycles (100 mA g−1) and demonstrates high reversible capacities of 125 mAh g−1 even under rates of 3200 mA g−1. LiNi0.925Ti0.05625O2 exhibits exceptional performance at electrode mass loadings (13.6 mg cm−2) comparable to those required for commercial cell applications.
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Jul 2025
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[30708, 30349]
Open Access
Abstract: Coordination nanosheets (CONASHs) or conjugated metal organic frameworks (MOFs) with distinctive metal-organic bonding structures exhibit promise for electronics, sensing, and energy storage. Porous Nickel-Benzene hexathiol complex (Ni-BHT) with noteworthy conductivity was first reported a decade ago, and recent synthetic modifications produced non-porous Ni-BHT with enhanced conductivity (≈50 S cm−1). Here the charge transport physics of such non-porous Ni-BHT films are studied with even higher conductivity (≈112 S cm−1). In contrast to the thermally activated electrical conductivity, thermoelectric measurements suggest an intrinsic metallic nature of Ni-BHT. It is shown that it is possible to tune the Fermi level and carrier polarity in Ni-BHT by electrolyte gating; gating is initially governed by the formation of an interfacial, electric double layer and then evolves into an electrochemical (de)doping process. These findings not only contribute to a deeper understanding of charge transport in CONASHs, but also show that Fermi level tuning is an effective approach for enhancing the thermoelectric performance of CONASHs.
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Jun 2025
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Open Access
Abstract: Frustrated Lewis pair (FLP) in heterogeneous chemistry have garnered tremendous attention in recent years owing to their diverse structural designs and outstanding activation ability for small molecules. The ability to tailor the structure of FLP enables precise control over their reactivity and selectivity, paving the way for the creation of catalysts for specific reactions. This review offers an in-depth examination of the design, characterization, and application of FLP within heterogeneous systems over the past few years. The current challenges in developing solid FLP catalysts are discussed. Furthermore, future potential advancements are explored, considering how emerging technologies and innovative approaches could enhance the design, advance characterization, and application of FLP in heterogeneous chemistry. Through this detailed overview, it is aimed to provide valuable insights into the evolving landscape of FLP research and its implications for the future applications in catalysis.
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Jun 2025
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I15-1-X-ray Pair Distribution Function (XPDF)
I21-Resonant Inelastic X-ray Scattering (RIXS)
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Diamond Proposal Number(s):
[35064, 39285, 40912]
Open Access
Abstract: Li-rich disordered rocksalts are promising next-generation cathode materials for Li-ion batteries. Recent reports have shown it is also possible to obtain Na-rich disordered rocksalts, however, it is currently poorly understood how the knowledge of the structural and redox chemistry translates from the Li-rich to the Na-rich analogs. Here, the properties of Li2MnO2F and Na2MnO2F are compared, which have different ion sizes (Li+ = 0.76 vs Na+ = 1.02 Å) but the same disordered rocksalt structure and stoichiometry. It is found that Na2MnO2F exhibits lower voltage Mn- and O-redox couples, opening access to a wider compositional range within the same voltage limits. Furthermore, the intercalation mechanism switches from predominantly single-phase solid solution behavior in Li2MnO2F to a two-phase transition in Na2MnO2F, accompanied by a greater decrease in the average Mn─O/F bond length. Li2MnO2F retains its long-range disordered rocksalt structure throughout the first cycle. In contrast, Na2MnO2F becomes completely amorphous during charge and develops a local structure characteristic of a post-spinel. This amorphization is partially reversible on discharge. The results show how the ion intercalation behavior of disordered rocksalts differs dramatically when changing from Li- to Na-ions and offers routes to control the electrochemical properties of these high-energy-density cathodes.
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May 2025
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