I18-Microfocus Spectroscopy
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Open Access
Abstract: Understanding magnetic domain wall (DW) dynamics is vital for improving the performance of heavy metal/ferromagnet based spintronic devices. Pd/Co/Pd multilayers hosting perpendicular magnetic anisotropy and interfacial Dzyaloshinskii-Moriya interaction are prototypes for high density magnetic memory devices. This work presents the creep regime DW dynamics in Pd/Co/Pd trilayers with Ta buffer layer excited by symmetric field-induced domain wall motion using Kerr microscopy. A systematic increment of DW velocity with increasing Co thickness is observed. SQUID-VSM measurements reveal that the effective anisotropy constant decreases with the Co layer, leading to an increased DW width. Kerr microscopy images confirm that the DW is becoming rougher with magnetic layer thickness because of the dominance of magnetostatic energy over the DW energy. Hard X-ray photoemission spectroscopy (HAXPES) reveals the presence of alloying at interfaces of Co/Pd. The asymmetry in magnetic circular dichroism HAXPES at the Pd 3d edge pictures the induced magnetic moment in Pd which is consistent with the larger saturation magnetization obtained from vibrating sample magnetometry. Extended X-ray absorption fine structure performed in out-of-plane and in-plane geometry shows the disordered nature of the Co local environment with the interdiffusion of Pd atoms into Co causing an asymmetry in the bonds.
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Feb 2025
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[30357]
Open Access
Abstract: 1,1,1-trifluoroethyl methyl carbonate (FEMC) is a popular non-flammable solvent for lithium-ion battery electrolytes, although its high irreversible capacity means it can only be used with film-forming additives like fluoroethylene carbonate (FEC). This work studies the origin of the high irreversible capacity of FEMC-containing cells. Scanning electron microscopy and Raman spectroscopy of graphite anodes after charging and discharging in an FEMC electrolyte show evidence of significant physical and chemical graphite degradation, likely caused by solvent co-intercalation, which is probably responsible for a large portion of the capacity loss. X-ray photoelectron spectroscopy analysis of the anodes shows very low graphite signals, a sign of graphite degradation, formation of a thick solid electrolyte interphase (SEI), or both. When a small amount of FEC is added to FEMC, co-intercalation does not occur. FEC reduction occurs at a higher potential versus Li/Li+ than FEMC co-intercalation. It also forms a significantly different and thinner SEI containing more carbon, less fluorine, and no apparent FEMC decomposition products.
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Sep 2024
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I09-Surface and Interface Structural Analysis
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Philip
Schädlich
,
Chitran
Ghosal
,
Monja
Stettner
,
Bharti
Matta
,
Susanne
Wolff
,
Franziska
Schölzel
,
Peter
Richter
,
Mark
Hutter
,
Anja
Haags
,
Sabine
Wenzel
,
Zamin
Mamiyev
,
Julian
Koch
,
Serguei
Soubatch
,
Philipp
Rosenzweig
,
Craig
Polley
,
Frank Stefan
Tautz
,
Christian
Kumpf
,
Kathrin
Küster
,
Ulrich
Starke
,
Thomas
Seyller
,
Francois C.
Bocquet
,
Christoph
Tegenkamp
Diamond Proposal Number(s):
[26188, 33755]
Open Access
Abstract: The synthesis of new graphene-based quantum materials by intercalation is an auspicious approach. However, an accompanying proximity coupling depends crucially on the structural details of the new heterostructure. It is studied in detail the Pb monolayer structure after intercalation into the graphene buffer layer on the SiC(0001) interface by means of photoelectron spectroscopy, x-ray standing waves, and scanning tunneling microscopy. A coherent fraction close to unity proves the formation of a flat Pb monolayer on the SiC surface. An interlayer distance of 3.67 Å to the suspended graphene underlines the formation of a truly van der Waals heterostructure. The 2D Pb layer reveals a quasi ten-fold periodicity due to the formation of a grain boundary network, ensuring the saturation of the Si surface bonds. Moreover, the densely-packed Pb layer also efficiently minimizes the doping influence by the SiC substrate, both from the surface dangling bonds and the SiC surface polarization, giving rise to charge-neutral monolayer graphene. The observation of a long-ranged (
) reconstruction on the graphene lattice at tunneling conditions close to Fermi energy is most likely a result of a nesting condition to be perfectly fulfilled.
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Jul 2023
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I09-Surface and Interface Structural Analysis
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Christopher H.
Don
,
Thomas P.
Shalvey
,
Matthew J.
Smiles
,
Luke
Thomas
,
Laurie J.
Phillips
,
Theodore D. C.
Hobson
,
Harry
Finch
,
Leanne A. H.
Jones
,
Jack E. N.
Swallow
,
Nicole
Fleck
,
Christopher
Markwell
,
Pardeep K.
Thakur
,
Tien-Lin
Lee
,
Deepnarayan
Biswas
,
Leon
Bowen
,
Benjamin A. D.
Williamson
,
David O.
Scanlon
,
Vinod R.
Dhanak
,
Ken
Durose
,
Tim D.
Veal
,
Jonathan D.
Major
Diamond Proposal Number(s):
[32696]
Open Access
Abstract: Despite the recent success of CdS/Sb2Se3 heterojunction devices, cadmium toxicity, parasitic absorption from the relatively narrow CdS band gap (2.4 eV) and multiple reports of inter-diffusion at the interface forming Cd(S,Se) and Sb2(S,Se)3 phases, present significant limitations to this device architecture. Among the options for alternative partner layers in antimony chalcogenide solar cells, the wide band gap, non-toxic titanium dioxide (TiO2) has demonstrated the most promise. It is generally accepted that the anatase phase of the polymorphic TiO2 is preferred, although there is currently an absence of analysis with regard to phase influence on device performance. This work reports approaches to distinguish between TiO2 phases using both surface and bulk characterization methods. A device fabricated with a radio frequency (RF) magnetron sputtered rutile-TiO2 window layer (FTO/TiO2/Sb2Se3/P3HT/Au) achieved an efficiency of 6.88% and near-record short–circuit current density (Jsc) of 32.44 mA cm−2, which is comparable to established solution based TiO2 fabrication methods that produced a highly anatase-TiO2 partner layer and a 6.91% efficiency device. The sputtered method introduces reproducibility challenges via the enhancement of interfacial charge barriers in multi-phase TiO2 films with a rutile surface and anatase bulk. This is shown to introduce severe S-shaped current–voltage (J–V) distortion and a drastic fill–factor (FF reduction in these devices.
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Jun 2023
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B22-Multimode InfraRed imaging And Microspectroscopy
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Diamond Proposal Number(s):
[14902, 25407]
Open Access
Abstract: Owing to their unique functionalities and tailorable properties that are unattainable in conventional materials, metal-organic frameworks (MOFs) have emerged as candidate materials for next-generation chemical sensors and optoelectronics. For instance, the ZnQ@OX-1 composite material, comprising a light-emitting guest encapsulated in the pores of the OX-1 framework, affords excellent sensing performance: a visible color change upon exposure to volatile acetone. In this work, a multimodal study on the exceptional vapochromism of this composite material using high-resolution spectroscopy techniques based on inelastic neutron scattering and synchrotron radiation is presented, supported by density functional theory calculations. While FTIR spectroscopy in the far-IR and mid-IR regions reveals the underlying interactions between ZnQ, OX-1, and acetone, the limit of detection at 50 ppm is determined through in situ gas dosing experiments using fluorescence spectroscopy. In addition, in situ gas dosing on the single crystal level is achieved with near-field infrared nanospectroscopy.
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Dec 2022
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Open Access
Abstract: Topological electronic materials hold great promise for revolutionizing spintronics, owing to their topological protected, spin-polarized conduction edge or surface state. One of the key bottlenecks for the practical use of common binary and ternary topological insulator materials is the large defect concentration that leads to a high background carrier concentration. Elemental tin in its α-phase is a room temperature topological semimetal, which is intrinsically less prone to defect-related shortcomings. Recently, the growth of ultrathin α-Sn films on ferromagnetic Co surfaces has been achieved; however, thicker films are needed to reach the 3D topological Dirac semimetallic state. Here, the growth of α-Sn films on Co at cryogenic temperatures was explored. Very low-temperature growth holds the promise of suppressing undesired phases, alloying across the interfaces, as well as the formation of Sn pillars or hillocks. Nevertheless, the critical Sn layer thickness of ≈3 atomic layers, above which the film partially transforms into the undesired b-phase, remains the same as for room-temperature growth. From ferromagnetic resonance studies, and supported by electron microscopy, it can be concluded that for cryogenic Sn layer growth, the interface between Sn and Co remains sharp and the magnetic properties of the Co layer stay intact.
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Oct 2022
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I11-High Resolution Powder Diffraction
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Dingyue
Hu
,
Karl
Dawson
,
Marco
Zanella
,
Troy D.
Manning
,
Luke M.
Daniels
,
Nigel D.
Browning
,
B. Layla
Mehdi
,
Yaobin
Xu
,
Houari
Amari
,
J. Felix
Shin
,
Michael J.
Pitcher
,
Ruiyong
Chen
,
Hongjun
Niu
,
Bowen
Liu
,
Matthew
Bilton
,
Junyoung
Kim
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Diamond Proposal Number(s):
[23666]
Open Access
Abstract: Performance durability is one of the essential requirements for solid oxide fuel cell materials operating in the intermediate temperature range (500–700 °C). The trade-off between desirable catalytic activity and long-term stability challenges the development and commercialization of electrode materials. Here an oxygen cathode material, Ba0.5Sr0.5(Co0.7Fe0.3)0.69−xMgxW0.31O3−δ (BSCFW-xMg), that exhibits excellent electrocatalytic performance through the addition of an optimized amount of Mg to the self-assembled nanocomposite Ba0.5Sr0.5(Co0.7Fe0.3)0.69W0.31O3−δ (BSCFW) by simple solid-state reaction is reported. Distinct from the bulk and surface approaches to introduce vacancies and defects in materials design, here the Mg2+ ions concentrate at the single perovskite/double perovskite interface of BSCFW with dislocations and Mg2+-rich nanolayers, resulting in stressed and compositionally inhomogeneous interface regions. The interfacial chemistry within these nanocomposites provides an additional degree of freedom to enable performance optimization over single phase materials and promotes the durability of alkaline-earth based fuel cell materials.
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Mar 2022
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[18570]
Open Access
Abstract: Planar organic heterostructures are widely explored and employed in photovoltaic cells, light-emitting diodes, and bilayer field-effect transistors. An important role for device performance plays the energy level alignment at the inorganic–organic and organic–organic interfaces. In this work, incremental ultraviolet photoelectron spectroscopy measurements and real-time X-ray scattering experiments are used to thoroughly investigate the thickness-dependent electronic and structural properties of a perfluoropentacene (PFP)-on-[6]phenacene heterostructure. For both materials an incremental increase of the material work function (positive interface dipole) is found. For [6]phenacene, this can be assigned to a thickness-dependent change of molecular arrangement evident from a change of the unit cell volume and a consequential alteration of the ionization energy. In the case of PFP the interface dipole stems from charge transfer from the substrate into unoccupied molecular orbitals resulting in an electrostatic potential on the surface. The magnitude of this potential can be correlated with an increased gap state density resulting from templated structural defects mediated by the bottom layer.
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Dec 2021
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I09-Surface and Interface Structural Analysis
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Diamond Proposal Number(s):
[26551]
Open Access
Abstract: For sodium-ion batteries, two pressing issues concerning electrolytes are flammability and compatibility with hard carbon anode materials. Non-flammable electrolytes that are sufficiently stable against hard carbon have—to the authors’ knowledge—previously only been obtained by either the use of high salt concentrations or additives. Herein, the authors present a simple, fluorine-free, and flame-retardant electrolyte which is compatible with hard carbon: 0.38 m sodium bis(oxalato)borate (NaBOB) in triethyl phosphate (TEP). A variety of techniques are employed to characterize the physical properties of the electrolyte, and to evaluate the electrochemical performance in full-cell sodium-ion batteries. The results reveal that the conductivity is sufficient for battery operation, no significant self-discharge occurs, and a satisfactory passivation is enabled by the electrolyte. In fact, a mean discharge capacity of 107 ± 4 mAh g−1 is achieved at the 1005th cycle, using Prussian white cathodes and hard carbon anodes. Hence, the studied electrolyte is a promising candidate for use in sodium-ion batteries.
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Oct 2021
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[18768, 22411]
Open Access
Abstract: Human society is facing—among other environmental threats—an enormous challenge due to human activities. The extensive use of high-tech devices and electronics equipment in the daily life makes, among others, rare-earth elements (REEs) recovery from secondary sources highly required. Here, a novel bioMOF-based single-walled carbon nanotube buckypaper (SWCNTBP) is presented as a new and efficient composite material (BioMOF@SWCNT-BP). The flexible and highly crystalline metal–organic framework (MOF), prepared from the natural amino acid L-threonine, has been homogeneously dispersed within the tangled net of a self-standing SWCNT-BP for lanthanides recovery from water. This MOF-carbon-based membrane exhibits high efficiency, either in static or dynamic regimes, in the recovery of lanthanides from aqueous streams outperforming the state-of-the-art. The capture performances of BPs are successfully improved after incorporation of such MOF featuring hexagonal functional channels decorated with the threonine amino acid residues, pointing toward the accessible void spaces, which boosts the capture properties of the final membrane, providing the adaptable functional environment to interact with lanthanides. This material's preparation presents also a potential for large-scale applications with a potential benefit on natural aquatic ecosystems as well. It is highly demanded because REEs from non-recycled waste materials are potential pollutants for surface waters.
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Aug 2021
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