I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[36180]
Abstract: Cr2GaC/C and V2PC/C MAX phase composites were synthesized via a free-radical polymerization–pyrolysis route, achieving > 87 wt% crystalline MAX phase content. SEM/EDS confirms the expected 2:1 atomic ratios of Cr:Ga and V:P, while BET analysis reveals structures with specific surface areas of 344 and 282 m2 g−1 for the Cr2GaC/C and V2PC/C composites, respectively, which are attributed to the porous carbonaceous network. HAXPES verifies core-level signatures consistent with the targeted MAX phases. This approach demonstrates the versatility of sol–gel-derived free-radical polymer networks as reactive precursors for MAX phase formation. The method further provides a foundation for advanced processing strategies, including vat photopolymerization-based additive manufacturing of high-surface-area and complex MAX phase architectures.
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Sep 2026
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I09-Surface and Interface Structural Analysis
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Eric S. A.
Goerlitzer
,
Zijia
Wu
,
Angus
Crookes
,
Shu
Hu
,
Rakesh
Arul
,
Sarah M.
Sibug-Torres
,
Bart
De Nijs
,
Reshma R.
Rao
,
Mary P.
Ryan
,
Angela
Demetriadou
,
Jeremy J.
Baumberg
Diamond Proposal Number(s):
[34784]
Open Access
Abstract: Controlling redox reactions at the atomic scale is key to enabling next-generation low-power memristive and neuromorphic devices. Ultrathin metallic layers, such as atomic monolayer palladium (Pd), offer tunable redox behavior well suited for switchable components in nanoscale electronics. Here, we present an in situ plasmonic-electrochemical platform that probes redox processes within subnanometer gaps using a nanoparticle-on-mirror (NPoM) geometry. Atomically thin Pd layers are grown by underpotential deposition, and their redox is monitored via surface enhanced Raman spectroscopy, revealing reversible transformations between metallic and dielectric Pd redox states. This confined plasmonic cavity enhances sensitivity to vibrational and electronic changes, allowing nondestructive optical readout of redox switching behaviors. By reducing the active switching volume to the monolayer limit while maintaining precise geometric control, this work establishes a powerful platform for probing redox dynamics at the atomic scale and points toward highly energy-efficient nanoswitches based on redox-active ultrathin materials.
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Sep 2026
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I09-Surface and Interface Structural Analysis
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Leyi
Loh
,
Han
Yan
,
Lixin
Liu
,
Yuan
Chen
,
Esther Lilian
Gray
,
Kamal Kumar
Paul
,
Deepnarayan
Biswas
,
Tien-Lin
Lee
,
Takashi
Taniguchi
,
Kenji
Watanabe
,
Mauro
Brotons-Gisbert
,
Yan
Wang
,
Manish
Chhowalla
Diamond Proposal Number(s):
[38012, 39914, 38086]
Open Access
Abstract: Unintentional doping from dielectrics can impact the electronic properties of two-dimensional transition metal dichalcogenide (2D TMD) semiconductors. Our recent work shows that high-dielectric-constant (k) ZrO2 is an electrostatically inert dielectric for 2D MoS2, supported by X-ray spectroscopy (XPS) and electrical measurements. Here, we expand this work through gate-controlled photoluminescence (PL) of monolayer MoS2 placed on different substrates. MoS2 on ZrO2 exhibits a low carrier concentration, indicated by a small trion-to-exciton ratio (X–/X0) of 0.5, similar to those on high-quality hBN. At a high electrostatic doping of ∼1013 cm–2, MoS2 on high-k ZrO2 reveals a slight exponential dependence of X–/X0 versus carrier concentration, while MoS2 on SiO2 shows strong exponential characteristics even at low gating (1012 cm–2) due to substantial electron doping from substrate-induced disorder tail states. Our findings provide insights into the doping mechanisms in industry-compatible amorphous dielectrics and evaluate their potential for scalable optoelectronic devices.
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Aug 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Diamond Proposal Number(s):
[43895]
Open Access
Abstract: X-ray photoelectron spectroscopy (XPS) is a major technique in catalyst research due to its ability to determine chemical states on the surface. Near ambient pressure XPS (NAP-XPS) enables in situ analysis, offering valuable insight into catalytic processes. However, modern catalysts are often supported on non-conductive supports such as TiO2 or SiO2, which can present significant challenges for XPS analysis due to charging and differential charging. These issues can distort spectral data, rendering data unusable and wasting valuable instrument time. While several sample preparation strategies exist, many are limited by not allowing high temperature analysis, the risk of sample loss (e.g., from powder flaking off), or continued susceptibility to charging. In this work, we introduce a simple, robust, and time-efficient method for mounting catalyst powders by compressing them between aluminium foil disks. This approach provides excellent sample hold, minimises charging effects, and is suitable for high-temperature NAP-XPS analysis and synchrotron x-ray sources. The method addresses key limitations of conventional preparation techniques and enables more reliable characterisation of insulating catalyst materials.
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Aug 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
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Lewis G.
Parker
,
Frances K.
Towers Tompkins
,
Jake M.
Seymour
,
Ekaterina
Gousseva
,
Christopher D.
Smith
,
Roger A.
Bennett
,
Pilar
Ferrer
,
David C.
Grinter
,
Claudia
Kolbeck
,
Dennis
Hein
,
Garlef
Wartner
,
Robert
Seidel
,
Denis
Céolin
,
Robert
Temperton
,
Robert G.
Palgrave
,
Richard P.
Matthews
,
Kevin R. J.
Lovelock
Diamond Proposal Number(s):
[33378, 35207, 36765, 36196]
Open Access
Abstract: Anion interactions with cations/molecules are crucial across chemistry and biology: in battery electrolytes, synthesis, atmospheric processes, and protein denaturation. Selecting the optimum anion represents an immense challenge, as anion interactions are diverse and complex. Descriptors are needed that quantitatively capture the ability of anions to interact with cations and molecules. However, only a small number of experimental anion interaction descriptors exist, all with similar limitations. Here we show that core-level anion electron binding energies, EB(core,anion), can be used to produce a new atomic-level descriptor for each of the key donor elements for anion interactions (O, N, F, Cl, Br, I, S), the element-specific donor number (DNE-XPS). DNE-XPS descriptors are intrinsic, capturing the anion interaction abilities independent of any probe, countercation, or solvent. DNE-XPS descriptors are also interpretable, as EB(core,anion) and therefore DNE-XPS are proportional to the electrostatic potential at the specific donor atom nucleus. Experimental core-level X-ray photoelectron spectroscopy (XPS) is used to measure EB(core,anion) and therefore DNE-XPS. Furthermore, DNE-XPS descriptors are produced easily and at low cost using lone-anion-SMD (solvation model density) calculations, a significant advance on the current anion descriptors, greatly reducing and potentially removing the need for experimental anion characterization. This work will greatly facilitate anion selection, especially for complex anions capable of forming interactions through multiple different atoms. We envisage our calculation method enabling the production of a very large database of DNE-XPS for each key element, ideal for use as machine learning training data sets.
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Aug 2026
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[36180]
Abstract: A correlation between depth-resolved defect chemistry and operando electrochemical response is established for compositionally graded gadolinia-doped ceria (GDC)/yttria-stabilized zirconia (YSZ) thin film electrodes. Integration of operando high-temperature scanning surface potential microscopy (HT-SSPM) with depth-resolved hard X-ray photoelectron spectroscopy (HAXPES) enables the relationship between bias-induced contact potential difference (CPD) evolution and spatially resolved Ce3+ distributions across the active film depth. While homogeneous GDC confines oxygen vacancies predominantly near the surface, compositionally graded architectures sustain a subsurface vacancy population extending toward the electrolyte interface. The fully graded structure exhibits steeper and more symmetric CPD gradients under both anodic and cathodic bias, consistent with balanced oxygen reduction and evolution kinetics. Depth-dependent HAXPES indicates that this electrochemical response correlates with enrichment of subsurface Ce3+ states rather than surface composition alone. These findings identify subsurface defect continuity as a key materials parameter influencing ionic transport and interfacial electrochemical behaviour in solid oxide electrodes.
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Aug 2026
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I09-Surface and Interface Structural Analysis
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Uday
Kushwah
,
Shiyang
Lu
,
Prajna
Bhatt
,
Aysha A.
Riaz
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Marco
Kirm
,
Vitali
Nagirnyi
,
Tanel
Käämbre
,
Johannes
Lischner
,
Anna
Regoutz
,
Juhan Matthias
Kahk
Diamond Proposal Number(s):
[36189]
Open Access
Abstract: Ultrafast scintillators based on ternary hexafluorides are promising for next-generation radiation detectors, which can be used in time-of-flight positron emission tomography. To gain a detailed understanding of the scintillation mechanism in these materials, accurate knowledge of the electronic band structure is required. In this study, photoelectron spectroscopy, density-functional theory, and G0W0 calculations were used to investigate the electronic structure of K2SiF6. The G0W0 calculations predict a wide band gap of 12.4 eV reflecting the strongly ionic character of the bonding. In contrast to predictions from semi-local or hybrid density-functional theory calculations, the large band gap predicted by G0W0 suggests that Auger-Meitner decay of K 3p holes is energetically not allowed and that scintillation via cross-luminescence is possible in this material. However, the poor light-yield observed experimentally indicates that the exclusion of Auger-Meitner decay is not sufficient for good scintillation performance, and cross-luminescence competes with other decay channels.
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Jul 2026
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I09-Surface and Interface Structural Analysis
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Galo J.
Paez Fajardo
,
Daniela E.
Dogaru
,
Hrishit
Banerjee
,
Muhammad
Ans
,
Matthew J. W.
Ogley
,
Veronika
Majherova
,
Gerard
Bree
,
Innes
Mcclelland
,
Shohei
Hayashida
,
Pascal
Puphal
,
Masahiko
Isobe
,
Bernhard
Keimer
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Dave C.
Grinter
,
Pilar
Ferrer
,
Serena A.
Cussen
,
Matthias
Hepting
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[33459, 35075, 36917, 30201]
Open Access
Abstract: Describing lithium-based battery positive electrodes based on different transition metal or oxygen-redox regimes can cause confusion in understanding metal–ligand hybridization, oxygen dimerization and degradation processes. Therefore, it is urgent to investigate the electronic structure of these materials and identify the role each cation and anion has in charge compensation at the subnanoscale. Here, using X-ray resonance photoemission spectroscopy, single-impurity Anderson models, spectral simulations and theoretical calculations, we examine redox mechanisms in positive electrodes during lithium-based battery operation. This approach reconciles the redox description of two positive electrode active materials—LiMn0.6Fe0.4PO4 and LiNiO2—in terms of varying degrees of charge transfer using the Zaanen–Sawatzky–Allen framework. In LiMn0.6Fe0.4PO4, the lack of strong hybridization indicates that the capacity results from the depopulation of metal 3d states, that is, conventional metal redox. However, in cells with LiNiO2-based positive electrodes, negative charge transfer dominates, and redox occurs through the formation and elimination of ligand-hole states. These results clarify the role of oxygen in Ni-rich systems and provide a framework to explain how the charge/discharge capacities are linked to oxygen-dominated states in highly covalent systems, without the need to consider oxygen dimerization.
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Jun 2026
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Jad
Jaafar
,
Ye
Fan
,
Maryam
Kazemzadeh-Atoufi
,
Ryo
Mizuta
,
Jinfeng
Yang
,
Jack E. N.
Swallow
,
Elizabeth
Jones
,
Matthijs A.
Van Spronsen
,
Georg
Held
,
Robert S
Weatherup
,
Peter
Voorhees
,
David J.
Wales
,
Gabor
Csanyi
,
Stephan
Hofmann
Diamond Proposal Number(s):
[25633]
Open Access
Abstract: The commercialization of emerging materials is hindered by the empirical nature of process development, with the underpinning solid-state reaction kinetics remaining elusive due to their inherent multistep and multiscale character and the vast configurational and parameter space. We combine high-throughput operando scanning electron microscopy (OSEM) with extended classical continuum and phase-field simulations and atomistic machine-learned interatomic potential (MLIP) surrogate models to demonstrate effective foundational reaction exploration, using thermal oxidation of chemical-vapor-deposited monolayer WS2 across a temperature range of 450–680 °C as our benchmark reaction. OSEM provides statistically relevant reaction data sets of spatiotemporal basal plane nucleation kinetics and propagation of tens of thousands of individual 1D reaction facets, revealing time-dependent rates. By extending Avrami theory and employing a calibrated phase-field model, we extract an apparent nucleation barrier of 1.1 eV and show that the complex rate behavior arises from mixed reaction–diffusion control. Atomistic reaction exploration via MLIPs guided by these experimental data reveals that oxidative reaction chains leading to W volatilization and etch pit formation are driven not by the most common sulfur or substitutional oxygen point defects but by more complex defects such as W vacancies. MLIP diffusion barrier screening identifies the role of chemisorbed hydroxyl species for this reaction scenario, while systematic screening of 1D edge configurations and their terminations uncovers the structural origins of the pronounced in-plane reaction anisotropies. We discuss the potential of our synergistic approach to effectively bring experimental and computational approaches closer together and accelerate critically required process discovery for advanced materials.
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May 2026
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Diamond Proposal Number(s):
[28149]
Open Access
Abstract: High- and medium-entropy alloys (HMEAs) are emerging as promising catalysts due to their different electronics and very good thermal stability. HMEAs have already exhibited remarkable catalytic performance in several electrocatalytic reactions involving small molecules; however, their use in thermal complex organic reactions is still in its infancy. Herein, we present a highly dense supported HMEA material (≈50 wt% in metal) prepared by the pyrolysis of a metal–organic framework (MOF), used as a template in virtue of its well-spaced single metal atoms, to obtain catalytic carbon-supported nano-HMEAs in a particle-to-particle synthetic way. The solid material shows a remarkable catalytic activity for alkene oxidation reactions and can be recycled at least 10 times; however, a higher activity of the monometallic catalysts in terms of the turnover number is found. These results constitute, to our knowledge, one of the first examples of catalytic HMEAs for organic synthesis.
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May 2026
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