B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B18-Core EXAFS
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Yifeng
Wang
,
Eleanor
Ender
,
Santosh
Kumar
,
Cindy
Tseng
,
Guangmeimei
Yang
,
Boxi
Ye
,
Caiwu
Liang
,
Youli
Yu
,
Norton
West
,
Inderjeet
Chauhan
,
Jun H.
Ng
,
Sid
Halder
,
Sang Gu
Ji
,
Georg
Held
,
Mary P.
Ryan
,
Katie L.
Moore
,
Alex S.
Walton
,
Reshma R.
Rao
Diamond Proposal Number(s):
[42239, 41758, 39622, 37550, 42151]
Open Access
Abstract: Nickel-based cathodes are widely used in alkaline water electrolysis, yet the nature and stability of the active surface under operating conditions remains unclear. In particular, the role of metal/oxo–hydroxo interfacial structures in governing hydrogen evolution activity is not well understood. Here, we employ a multimodal, depth-sensitive approach combining operando Ni L-edge X-ray absorption spectroscopy, depth-sensitive X-ray absorption measurements in total electron yield and Auger electron yield modes, X-ray photoelectron spectroscopy, isotopically labeled nano secondary ion mass spectrometry, and online electrochemical mass spectrometry to directly track the evolution of Ni/NiOxHy interfaces during the hydrogen evolution reaction. Using well-defined sputtered Ni thin films as a model system, we show that progressive reduction of near-surface oxide/hydroxide species is accompanied by a gradual loss of hydrogen evolution activity. Depth-resolved measurements reveal a predominantly metallic outermost surface under cathodic bias, while NiOxHy forms on the surface upon relaxation to open-circuit conditions. Importantly, mild anodic pre-conditioning regenerates subsurface NiOxHy species, resulting in a sustained increase in hydrogen evolution activity upon subsequent cathodic polarization. These results establish the crucial role of metal/oxo–hydroxo interfaces as active phases for hydrogen evolution and provide a framework for engineering robust, Earth-abundant HER cathodes capable of operating under dynamic, real-world electrolysis conditions.
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Aug 2026
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Optics
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Open Access
Abstract: The precise exploitation and efficient control of residual stresses are crucial for the development of high-performance thin-film optics. Multi-beam optical sensors (MOS) have been widely used for in situ residual stress measurements; however, this only provides information on the average residual stress at a single position. To overcome this limitation, speckle-based curvature optical metrology (SCOM) has been implemented at the multilayer deposition system (MDS) at Diamond Light Source. SCOM delivers two-dimensional curvature mapping, which has enabled direct visualization of the variation of spatial residual stress and substrate deformation for the first time. Benchmarking of SCOM measurements against MOS reveals excellent agreement in the extracted curvature for a deformable mirror. Importantly, SCOM offers a significantly larger dynamic range, allowing accurate measurements under the extreme curvature conditions that are frequently encountered in thick, high-residual stress films. This approach was also used to evaluate the residual stress evolution of a range of important materials, including Mo, Si and WSi2, which have been systematically investigated across varying deposition thicknesses and working pressures.
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Aug 2026
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E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[38966]
Open Access
Abstract: Mixed-cation lead mixed-halide perovskites are promising materials for applications in photovoltaics; however, it has been suggested that they exhibit instabilities linked to nanoscale heterogeneity. Directly probing the origins of this heterogeneity requires characterization with nanoscale spatial resolution, making transmission electron microscopy (TEM) an essential tool. However, characterizing these materials is challenging due to their extreme sensitivity to electron irradiation. Here, we develop a low-dose, concurrent methodology using four-dimensional scanning transmission electron microscopy (4D-STEM) and energy-dispersive x-ray spectroscopy (EDX) in order to map both the chemical and structural architecture of a (FA0.83Cs0.17)Pb(I0.8Br0.2)3 perovskite film without inducing damage. Our correlative analysis reveals a complex mosaic of coexisting crystal structures in this state-of-the-art LHP film. We establish a direct link between local chemical composition and crystal structure, showing that the formation of undesirable, photovoltaically inactive hexagonal polytypes is predominantly driven by local deficiencies in the stabilizing cesium cation. These findings provide crucial insight into one of the fundamental origins of structural instabilities in mixed composition perovskite thin-films, suggesting that achieving long-term device performance requires the development of fabrication routes that ensure compositional homogeneity at the nanoscale.
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Jul 2026
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E01-JEM ARM 200CF
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Emerson C.
Kohlrausch
,
Christopher
Leist
,
Gazi N.
Aliev
,
Mohsen
Danaie
,
Matthew
Young
,
Madasamy
Thangamuthu
,
Yifan
Chen
,
William J.
Cull
,
Wolfgang
Theis
,
Ute
Kaiser
,
Andrei N.
Khlobystov
,
Jesum
Alves Fernandes
Diamond Proposal Number(s):
[37379, 38763]
Abstract: Understanding how catalytically active sites emerge and evolve under working conditions is a fundamental challenge that limits the rational design of heterogeneous catalysts. Here, we directly visualize the transformation between alloyed PtNi and phase-separated Pt-NiO nanoclusters during hydrogen evolution. Using in situ low-voltage aberration-corrected electron microscopy, with the electron beam serving as both the stimulus and probe, we track the formation of active sites under low-water-vapor conditions. PtNi nanoclusters were assembled with controlled mixing of the atoms, resulting in two distinct configurational entropy states. Under reaction conditions, the transformation of bimetallic nanoclusters shifts from an entropically stabilized alloy to an enthalpically favored phase-separated configuration, controlled by oxygen availability and by a critical nucleus size. The atomic dynamics observed in real space correlate directly with catalytic performance, where the low-entropy Pt-NiO state achieves a record hydrogen evolution mass activity of 11.1 A/mgPt due to a high density of interfacial sites that promote water dissociation on NiO and efficient hydrogen adsorption on Pt atoms.
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Jun 2026
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I10-Beamline for Advanced Dichroism - scattering
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Roxana
Capu
,
Ryan
Thompson
,
C. Willem
Rischau
,
Marli R.
Cantarino
,
Premysl
Marsik
,
Sergey L.
Bud'Ko
,
Neven
Biškup
,
María
Varela
,
Yurii G.
Pashkevich
,
Serhii M.
Orel
,
Thomas
Prokscha
,
Andreas
Suter
,
Jiangtao
Zhao
,
Ugwumsinachi
Oji
,
Marco
Bonura
,
Peter
Bencok
,
Zaher
Salman
,
Stefano
Gariglio
,
Christian
Bernhard
,
Subhrangsu
Sarkar
Diamond Proposal Number(s):
[38112]
Open Access
Abstract: We report the dielectric and magnetic properties of epitaxial thin films of the high entropy oxide (HEO) perovskite Nd(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3, which orders magnetically below Tmag≈190 K. At T ≫ Tmag, the dielectric response reveals a Debye-type frequency dependence with a zero-frequency dielectric constant of
≈230–250. The dc bias voltage loops of
are reversible but exhibit three distinct peaks centred at zero and finite positive and negative voltage. We provide evidence that the zero-bias peak is governed by the oxygen sublattice while the finite bias peaks originate from cationic dipoles. The maximal response of the latter appears to be shifted to finite bias by a static uncompensated electric field due to a vertical gradient of the oxygen content. Below Tmag, this anomalous dielectric response is strongly suppressed, presumably by magnetostriction that counteracts and freezes the ionic displacements. These findings indicate a unique correlation between configurational entropy, dielectric response, and magnetic properties. In combination with a large dielectric strength, it enables a non-hysteretic tuning of the dielectric response of magnetoelectronic devices with multiple parameters like temperature, electric, and magnetic field. This HEO is equally interesting for fundamental studies of competing electric and magnetic orders in strongly disordered materials.
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Apr 2026
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I09-Surface and Interface Structural Analysis
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Lixin
Liu
,
Han
Yan
,
Leyi
Loh
,
Kamal Kumar
Paul
,
Soumya
Sarkar
,
Deepnarayan
Biswas
,
Tien-Lin
Lee
,
Takashi
Taniguchi
,
Kenji
Watanabe
,
Manish
Chhowalla
,
Yan
Wang
Diamond Proposal Number(s):
[38012, 39914]
Open Access
Abstract: Excellent gate electrostatics in field effect transistors (FETs) based on 2D transition metal dichalcogenide (2D TMD) channels can dramatically decrease static power dissipation. Energy-efficient FETs operate in enhancement mode with a small and positive threshold voltage (Vth) for n-type devices. However, most state-of-the-art FETs based on monolayer MoS2 channel operate in depletion mode with negative Vth due to doping from the underlying dielectric substrate. In this work, we identify key properties of the semiconductor/dielectric interface (MoS2 on industrially relevant high dielectric constant (k) HfO2, ZrO2 and hBN for reference) responsible for realizing enhancement-mode operation of 2D MoS2 channel FETs. We find that hBN and ZrO2 dielectric substrates provide low defect interfaces with MoS2 that enables effective modulation of the Vth using gate metals of different work functions (WFs). We use photoluminescence (PL) and synchrotron X-ray photoelectron spectroscopy (XPS) measurements to investigate doping levels in monolayer MoS2 on different dielectrics with different WF gate metals. We complement the FET and spectroscopic measurements with capacitance-voltage analysis on dielectrics with varying thicknesses, which confirms that Vth modulation in ZrO2 devices is correlated with WF of the gate metals – in contrast with HfO2 devices that exhibit signatures of Vth pinning induced by oxide/interface defect states. Finally, we demonstrate FETs using a 2D MoS2 channel and a 6 nm of ZrO2 dielectric, achieving a subthreshold swing of 87 mV dec−1 and a threshold voltage of 0.1 V. Our results offer insights into the role of dielectric/semiconductor interface in 2D MoS2 based FETs for realizing enhancement mode FETs and highlight the potential of ZrO2 as a scalable high-k dielectric.
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Mar 2026
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I15-Extreme Conditions
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Zhencai
Li
,
Zihao
Wang
,
Huotian
Zhang
,
Xuan
Ge
,
Ivan
Hung
,
Bozhao
Yin
,
Fengming
Cao
,
Pritam
Banerjee
,
Tianzhao
Xu
,
Lars R.
Jensen
,
Joerg
Jinschek
,
Morten M.
Smedskjaer
,
Zhehong
Gan
,
Laurent
Calvez
,
Guoping
Dong
,
Jianbei
Qiu
,
Donghong
Yu
,
Feng
Gao
,
Haomiao
Zhu
,
Yuanzheng
Yue
Diamond Proposal Number(s):
[39002]
Open Access
Abstract: Some zeolitic imidazolate frameworks (ZIFs) represent a new family of glass formers, with hitherto unknown photonic functionalities. In this work, we report the discovery of broadband white light emission in ZIF-62, achieved through a vitrification-pressurization-annealing strategy. In this strategy, visible (blue) light emission was realized after the vitrification of ZIF-62, subsequently enhanced and broadened upon pressurization. Additionally, a sharp redshift (37 nm) of the emission peak occurred in pressurized ZIF-62 glass as the annealing temperature exceeded a critical annealing temperature (1.07Tg). This implies that the photoluminescence of ZIF-62 can be precisely tailored. The photoluminescence quantum yield of ZIF-62 glass reached 12.2% after annealing at 1.13Tg for 30 min. The origin of the observed phenomena was revealed by conducting structural analyses. Based on the annealed ZIF-62 glass with the best photoluminescent performance, a white light-emitting diode (LED) was fabricated, which exhibited a luminous efficacy of 4.2 lm/W and a high operational stability, i.e., retaining 36.8% of the efficacy after 72 h of operation. This work demonstrated the feasibility of the development of one-component white LEDs by utilizing the annealed ZIF-62 glass.
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Mar 2026
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I11-High Resolution Powder Diffraction
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Ziqin
Jiao
,
Tao
Zeng
,
Wenhai
Ji
,
Zheng
Liu
,
Wenguang
Zhao
,
Xiaoyu
Gao
,
Yongbiao
Mu
,
Xuansi
Jiang
,
Yubin
Li
,
Guojie
Chen
,
Wenqing
Yao
,
Jinqi
Li
,
Ze
He
,
Juping
Xu
,
Ping
Miao
,
Wen
Yin
,
Yuguang
Pu
,
Rui
Wang
,
Yinguo
Xiao
Diamond Proposal Number(s):
[34243]
Abstract: Lattice-oxygen redox (L-OR) has been widely considered a viable approach to attain high-capacity cathodes for next-generation batteries. However, achieving highly reversible L - OR remains challenging due to the intrinsic chemical instability of lattice oxygen. As such, stabilizing the lattice oxygen becomes necessary for improving the performance of cathode materials with oxygen redox chemistry. In this study, the distinct properties of both bulk and surface lattice oxygen are systematically studied in a model Li-rich layered oxide material (LRMO, i.e., Li1.2Ni0.2Mn0.6O2) by employing different techniques. We find that, in the bulk, distortions in octahedral coordination geometry are closely correlated with variations in the electronic structure, and the substitution of Li ions with protons in a subsurface layer enhances the stability of surface lattice oxygen by altering its coordination environment. By jointly regulating the local environments of both bulk and surface lattice oxygen, the initial Coulombic efficiency is remarkably improved from 73.88% to 91.72%. Moreover, the modified LRMO demonstrates an impressive cycle stability, which realizes a capacity retention of 95.9% after 500 cycles at 250 mA g−1. This work demonstrates that rationally-designed local environments of lattice oxygen can effectively stabilize the oxygen redox in Li-rich cathodes.
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Feb 2026
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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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