I09-Surface and Interface Structural Analysis
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Muhammad
Ans
,
Eleni
Fiamegkou
,
Ashok S.
Menon
,
Gaurav C.
Pandey
,
Gaolo J.
Paez Fajardo
,
Harry
Gillions
,
Paolo
Melgari
,
Calum
Clenahan
,
Satish
Bolloju
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Serena A.
Cussen
,
Beth I. J.
Johnston
,
Louis F. J.
Piper
Diamond Proposal Number(s):
[38340]
Open Access
Abstract: Lithium nickel oxide (LNO) cathodes offer high capacity for high-energy-density applications but suffer rapid degradation above 4.2 V due to surface and bulk instabilities. Here, we apply an ultrathin aluminum oxide coating using powder atomic layer deposition to improve surface stability. Pouch cell testing shows that coated LNO delivers improved cycling behavior, retaining 91.2% capacity after 100 cycles at C/3. Operando X-ray diffraction reveals that after aging, coated LNO undergoes a less kinetically hindered delithiation, indicating that the surface coating further provides a surface-to-bulk stabilization effect. Postmortem surface sensitive spectroscopy confirms that the aluminum oxide layer (1) scavenges hydrofluoric acid and (2) suppresses surface reconstruction, reducing impedance growth and improving the surface integrity. Overall, the results demonstrate that ultrathin aluminum oxide coatings effectively mitigate interfacial degradation and enhance bulk electrochemical kinetics, providing an effective and scalable approach toward improving the long-term performance of ultra-Ni-rich cathodes.
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Mar 2026
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[31857]
Open Access
Abstract: The transition to non-flammable electrolytes is essential to enhance the safety of rechargeable lithium-ion batteries in the context of rapid global electrification. However, these next-generation electrolytes often exhibit inferior electrochemical performance compared to conventional carbonate-based systems, hindering their practical application. Recent studies suggest that pre-passivating electrodes with conventional electrolytes can enhance performance for some next-generation electrolytes through interphase stabilization, yet a mechanistic understanding of this improvement remains to be established. In this work, we combine detailed electrochemical analysis with synchrotron-based hard X-ray photoelectron spectroscopy to investigate how pre-passivated electrodes influence the stability and performance of cells containing non-flammable electrolytes based on the solvent methyl(2,2,2-trifluoroethyl) carbonate (FEMC). We identify the anode solid electrolyte interphase (SEI) as the critical limiting factor towards use of FEMC electrolytes, with pre-passivation in conventional electrolytes significantly mitigating continuous electrolyte decomposition. Furthermore, our results show that the cathode electrolyte interphase (CEI) also plays a vital role, and that optimal performance is achieved by combining an SEI formed in a conventional electrolyte with a CEI formed in the FEMC electrolyte. These findings provide direct electrochemical and spectroscopic evidence for interphase-driven performance improvements, offering a practical pathway to advance non-flammable electrolyte technologies.
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Feb 2026
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I09-Surface and Interface Structural Analysis
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Isabel
Huck
,
Niels
Kubitza
,
Tom
Keil
,
Marius
Schlapp
,
Robert
Winkler
,
Prajna
Bhatt
,
Christoph
Schlueter
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Paweł P.
Michałowski
,
Leopoldo
Molina-Luna
,
Anna
Regoutz
,
Christina S.
Birkel
Diamond Proposal Number(s):
[36180]
Abstract: MAX phases are an extremely versatile family of layered compounds that usually consist of an early to-mid transition metal (M-element), a main group element (mainly groups 13–15) or late transition metal (A-element) and carbon and/or nitrogen (X-element). It is therefore not too surprising that in addition to the roughly 70 compounds with 211 stoichiometry, there exist many solid solutions with mixed elements on the M- and A-site, respectively. Much less common are solid solution phases with mixed elements on both M- and A-site simultaneously (double-site solid solutions), as well as solid solutions on the X-site (carbonitride MAX phases). Challenging these restrictions in the chemical composition space, we present here for the first time (V0.2Cr0.8)2(Ga0.5Ge0.5)(C0.6N0.4) as a new carbonitride member of the MAX phase family, containing solid solutions on all three lattice sites simultaneously. This triple-site solid solution MAX phase is synthesized by high-temperature solid-state methods, and we demonstrate that it is possible to use two different nitrogen-containing precursors (VN and Cr2N), respectively. Structure, morphology and chemical composition are characterized by X-ray powder diffraction (XRD), electron microscopy (SEM/TEM), secondary ion mass spectrometry (SIMS), and X-ray photoelectron spectroscopy (HAXPES).
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Feb 2026
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I09-Surface and Interface Structural Analysis
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Arya
Loloee
,
Manuel
Scharrer
,
Tullio S.
Geraci
,
Hui-Fei
Zhai
,
Matt S.
Flores
,
Prajna
Bhatt
,
Aysha A.
Riaz
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Anna
Regoutz
,
Jakoah
Brgoch
,
Jason F.
Khoury
,
Alexandra
Navrotsky
,
Christina S.
Birkel
Diamond Proposal Number(s):
[34325]
Abstract: MAX phases are a class of compounds known for having both metallic and ceramic properties, such as good electrical conductivity, oxidation resistance, and high hardness. The bulk of the research on their properties focuses on those with titanium at the M-site and metals from groups 13 to 15, e.g., aluminum, at the A-site. Here, we expand the properties repertoire with new arsenic-containing A-site solid solutions, V2(As1–xPx)C and V2(As1–xGex)C. The structure and elemental composition of the solid solutions were resolved with powder X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and hard X-ray photoelectron spectroscopy. The electrical resistivity measurements show that both full series are metallic with the parent phases being the most conductive. Thermal analyses show V2GeC is the most oxidation resistant and V2AsC is the least, while substitutions decrease thermal stability, as oxidation resistance of the intermediate compositions shifts toward that of V2AsC. The V2(As1–xGex)C series shows little variation in hardness across compositions, while the incorporation of phosphorus noticeably increases hardness.
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Jan 2026
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I09-Surface and Interface Structural Analysis
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Prajwal M.
Laxmeesha
,
Rajesh
Dutta
,
Rajeev Kumar
Rai
,
Sharup
Sheikh
,
Michael F.
Discala
,
Uditha M.
Jayathilake
,
Alexander
Velič
,
Tarush
Tandon
,
Tessa D.
Tucker
,
Christoph
Klewe
,
Haile
Ambaye
,
Timothy
Charlton
,
Tien-Lin
Lee
,
Eric A.
Stach
,
Kemp W.
Plumb
,
Alexander X.
Gray
,
Steven J.
May
Diamond Proposal Number(s):
[40454]
Abstract: Kagome metals are an intriguing class of quantum materials as the presence of both flat bands and Dirac points provides access to functional properties present in strongly correlated and topological materials. To fully harness these electronic features, the ability to tune the Fermi level relative to the band positions is needed. Here, we explore the structural, electronic, and magnetic impacts of substitutional alloying within ferromagnetic kagome metal Fe3Sn2 in thin films grown by molecular beam epitaxy. Transition metals, Mn and Co, are chosen as substitutes for Fe to reduce or increase the d-band electron count, thereby moving the Fermi level accordingly. We find that Co is not incorporated into the Fe3Sn2 structure but instead results in a two-phase Fe–Co and (Fe,Co)Sn composite. In contrast, Fe3−xMnxSn2 films are realized with x of up to 1.0, retaining crystalline quality comparable with the parent phase. The incorporation of Mn repositions the flat bands relative to the Fermi level in a manner consistent with hole-doping, as revealed by hard x-ray photoemission and density functional theory. The Fe3−xMnxSn2 films retain room temperature ferromagnetism, with x-ray magnetic circular dichroism measurements confirming that the Fe and Mn moments are ferromagnetically aligned. The ability to hole-dope this magnetic kagome metal provides a platform for tuning properties, such as anomalous Hall and Nernst responses.
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Jan 2026
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I09-Surface and Interface Structural Analysis
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Yue
Yu
,
Xu
Zhang
,
Wenjing
Xu
,
Rongkun
Chen
,
Cien
Liu
,
Yiru
Zhao
,
Yushuo
Hu
,
Zhilai
Fang
,
Ning
Jia
,
Xiangyu
Xu
,
Kelvin H. L.
Zhang
Diamond Proposal Number(s):
[37428]
Abstract: GaN-based deep ultraviolet (DUV) optoelectronic devices have garnered considerable attention for applications in sterilization, biological detection, and optical communications. However, the performance of current DUV optoelectronic devices is limited by the insufficient DUV transparency of conventional electrodes. In this work, the epitaxial growth of degenerately Si-doped Ga2O3 films on GaN as a promising DUV transparent electrode is reported. The 0.5% Si doped Ga2O3 (n+-Ga2O3) films exhibit DUV transparency exceeding 85% in the spectral range from 280 to 400 nm wavelength. Such a high DUV transparency is attributed to the ultrawide bandgap of ≈5.0 eV of the n+-Ga2O3 film induced by the Burstein–Moss effect due to degenerate doping. Moreover, the n+-Ga2O3 film exhibits a very low specific contact resistance of 1.96 × 10−4 Ω cm2 to GaN. High-resolution X-ray photoemission spectroscopic (XPS) study reveals that n+-Ga2O3 forms a type-II staggered band alignment with GaN with a low interface barrier of 0.15 eV and a narrow band bending thickness of a few nm. The small barrier, together with the degenerately doped Ga2O3 film, enables excellent electrical contact at the n+-Ga2O3/GaN interface and low contact resistance. This work demonstrates n+-Ga2O3 as a promising alternative for DUV transparent electrode for GaN-based DUV devices.
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Jan 2026
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B18-Core EXAFS
E01-JEM ARM 200CF
I09-Surface and Interface Structural Analysis
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Thomas J.
Liddy
,
Benjamin J.
Young
,
Emerson C.
Kohlrausch
,
Andreas
Weilhard
,
Gazi N.
Aliev
,
Yifan
Chen
,
Manfred E.
Schuster
,
Mohsen
Danaie
,
Luke L.
Keenan
,
Donato
Decarolis
,
Diego
Gianolio
,
Siqi
Wang
,
Mingming
Zhu
,
Graham J.
Hutchings
,
David M.
Grant
,
Wolfgang
Theis
,
Tien-Lin
Lee
,
David A.
Duncan
,
Alberto
Roldan
,
Andrei N.
Khlobystov
,
Jesum
Alves Fernandes
Diamond Proposal Number(s):
[38764]
Open Access
Abstract: Ammonia is an attractive hydrogen carrier, yet its practical use is limited by the need for efficient catalytic decomposition. We demonstrate that in-situ N-doping of Ru nanoparticles and graphitized carbon nanofiber supports during reaction produces a sharp increase in hydrogen production during the first 40 h, followed by stable activity. Spectroscopic and microscopic analyses, together with density functional theory simulations, reveal that Ru nitridation is rapid and support-independent, resulting in a mechanistic shift from the traditional Langmuir–Hinshelwood to a Mars–van Krevelen pathway, further confirmed by isotopic labelling experiments. In contrast, the progressive nitridation of the carbon support, observed via X-ray photoelectron spectroscopy, modulates the electronic environment of Ru and functions as a dynamic nitrogen reservoir that enables reversible N atoms exchange with the Ru particles, facilitating N desorption from the Ru surface and thereby governing the catalytic activity enhancement. These new findings provide new mechanistic insight into ammonia decomposition and establish progressive nitrogen doping of carbon supports as a strategy for designing efficient metal-based catalysts for hydrogen production.
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Dec 2025
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I09-Surface and Interface Structural Analysis
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G.
Cicconi
,
M.
Bosi
,
F.
Mezzadri
,
A.
Ugolotti
,
I.
Cora
,
L.
Seravalli
,
H.
Tornatzky
,
J.
Lähnemann
,
M. R.
Wagner
,
P.
Bhatt
,
P. K.
Thakur
,
T.-L.
Lee
,
A.
Regoutz
,
A.
Baraldi
,
D.
Bersani
,
L.
Cademartiri
,
A.
Parisini
,
B.
Pécz
,
L.
Miglio
,
R.
Fornari
,
P.
Mazzolini
Diamond Proposal Number(s):
[36180]
Open Access
Abstract: The ultra-wide bandgap semiconductor rutile germanium oxide (r-GeO2, Eg ≈ 4.6 eV) is gaining momentum in the quest for novel materials for power electronics. In this work, we experimentally and theoretically investigate the physical mechanisms behind the nucleation and growth of epitaxial (001) r-GeO2 on isostructural r-TiO2 substrates via metalorganic vapor phase epitaxy (MOVPE) using isobutylgermane and O2 precursors. In the identified deposition window, the thin film growth seems to be affected by partial GeO suboxide desorption, and we observe that the layers are always composed of r-GeO2 islands embedded and/or surrounded by amorphous material. Ge/Ti interdiffusion at the epilayer-substrate interface is found at the base of each r-GeO2 island; combining experimental analysis and multiscale theoretical simulations we discuss how such a process is fundamental to achieve partial strain mitigation allowing for the nucleation of epitaxial r-GeO2 and suggest in this regard a limiting threshold to avoid the formation of amorphous material. Moreover, we shed light on the formation of different facets in r-GeO2 at early stages of growth and after merging of islands.
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Dec 2025
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[29113]
Open Access
Abstract: LiNi0.5Mn1.5O4 (LNMO) cathodes offer a cobalt-free, high-voltage alternative to current state-of-the-art Li-ion battery cathodes, and are particularly well-suited for high-power applications due to their 3D lithium-ion pathways and structural stability. However, degradation of commercial electrolytes at high voltages exacerbates capacity decay, as instability at the cathode surface causes active material loss, surface reconstructions, thickening surface layers, and increases in internal cell resistance. Cationic substitution has been proposed to enhance surface stability, thus limiting capacity decay. Here, we demonstrate the stabilizing effect of Mg on the LNMO cathode surface, which is most evident during the early stages of cycling. This study indicates that improved O 2p-TM 3d hybridization in Mg-substituted LNMO, facilitated by Li-site defects, leads to the formation of a stable surface layer that is corrosion-resistant at high voltage. Examination of Fe-substituted and unsubstituted LNMO further confirms that the surface stability is uniquely enabled by Mg substitution. This work offers valuable insights into surface design for reducing degradation in high-voltage spinel cathodes.
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Nov 2025
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I09-Surface and Interface Structural Analysis
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Wenjing
Xu
,
Hailing
Guo
,
Zhenni
Yang
,
Yihong
Chen
,
Xiangyu
Xu
,
Tien-Lin
Lee
,
Duanyang
Chen
,
Xinxin
Yu
,
Yuzheng
Guo
,
Zhaofu
Zhang
,
Hongji
Qi
,
Kelvin H. I.
Zhang
Diamond Proposal Number(s):
[37428]
Abstract: In this work, we investigate the electronic structure and interfacial band alignment of β-(Al𝑥Ga1−𝑥)2O3/Ga2O3 heterojunctions using a combination of synchrotron-based hard x-ray photoemission spectroscopy (HAXPES) and first-principles hybrid density functional theory calculations. β-(Al𝑥Ga1−𝑥)2O3 films with Al compositions of x = 0.12, 0.19, and 0.29 were grown on Fe-doped β-Ga2O3 (010) substrates via pulsed laser deposition. The band gap of β-(Al𝑥Ga1−𝑥)2O3 increases from (4.83 ± 0.05) eV (x = 0) to (5.37 ± 0.08) eV (x = 0.29), primarily driven by an upward shift of the conduction band edge due to hybridization between Al 3s and Ga 4s states, while the valence band edge exhibits a slight downward shift. Both experimental HAXPES data and theoretical calculations confirmed the formation of a “type I” (straddling) band alignment in the β-(Al𝑥Ga1−𝑥)2O3/Ga2O3 heterojunctions. For instance, at x = 0.29, the conduction band offset and valence band offset are approximately 0.33 and 0.21 eV, respectively. These findings provide valuable insights for designing modulation-doped β-(Al𝑥Ga1−𝑥)2O3/Ga2O3 heterostructures, enabling the realization of a two-dimensional electron gas and its application in high-frequency electronic devices.
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Oct 2025
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