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43 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I07-Surface & interface diffraction I09-Surface and Interface Structural Analysis	Direct experimental evidence for substrate adatom incorporation into a molecular overlayer Philip J. Mousley , Luke A. Rochford , Paul T. P. Ryan , Philip Blowey , James Lawrence , David A. Duncan , Hadeel Hussain , Billal Sohail , Tien-Lin Lee , Gavin R. Bell , Giovanni Costantini , Reinhard J. Maurer , Christopher Nicklin , D. Phil Woodruff The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.2c01432 Diamond Proposal Number(s): [14884, 4884] Open Access Show Abstract ▼ Abstract: While the phenomenon of metal substrate adatom incorporation into molecular overlayers is generally believed to occur in several systems, the experimental evidence for this relies on the interpretation of scanning tunneling microscopy (STM) images, which can be ambiguous and provides no quantitative structural information. We show that surface X-ray diffraction (SXRD) uniquely provides unambiguous identification of these metal adatoms. We present the results of a detailed structural study of the Au(111)-F4TCNQ system, combining surface characterization by STM, low-energy electron diffraction, and soft X-ray photoelectron spectroscopy with quantitative experimental structural information from normal incidence X-ray standing wave (NIXSW) and SXRD, together with dispersion-corrected density functional theory (DFT) calculations. Excellent agreement is found between the NIXSW data and the DFT calculations regarding the height and conformation of the adsorbed molecule, which has a twisted geometry rather than the previously supposed inverted bowl shape. SXRD measurements provide unequivocal evidence for the presence and location of Au adatoms, while the DFT calculations show this reconstruction to be strongly energetically favored.	Apr 2022
I07-Surface & interface diffraction	Interfacial rearrangements and strain evolution in the thin film growth of ZnPc on glass Thomas L. Derrien , Andreas E. Lauritzen , Pascal Kaienburg , Ellis Hancox , Chris Nicklin , Moritz Riede Physical Review Materials 6 DOI: 10.1103/PhysRevMaterials.6.033401 Diamond Proposal Number(s): [20426] Open Access Show Abstract ▼ Abstract: We report on the characterization of the growth of vacuum-deposited zinc phthalocyanine (ZnPc) thin films on glass through a combination of in situ grazing incidence x-ray scattering, x-ray reflectivity, and atomic force microscopy. We found that the growth at room temperature proceeds via the formation of two structurally unique substrate-induced interfacial layers, followed by the growth of the γ -ZnPc polymorph thereafter (thickness ≈ 1.0 nm). As the growth of the bulk γ -ZnPc progresses, a substantial out-of-plane lattice strain ( ≈ 15 % relative to γ -ZnPc powder) is continually relaxed during the thin film growth. The rate of strain relaxation was slowed after a thickness of ≈ 13 nm, corresponding to the transition from layer growth to island growth. The findings reveal the real-time microstructural evolution of ZnPc and highlight the importance of substrate-induced strain on thin film growth.	Mar 2022
	Synchrotron techniques for African research and technology: a step-change in structural biology and energy materials Chris Nicklin , Rebekka Stredwick , Trevor Sewell Synchrotron Radiation News DOI: 10.1080/08940886.2022.2043684 Open Access Show Abstract ▼ Abstract: In June 2021, scientists celebrated the numerous achievements of a unique collaboration between researchers from the UK and Africa and the UK’s national synchrotron, Diamond Light Source [1]. The Synchrotron Techniques for African Research and Technology (START) [2] programme was funded by a 3-year, £3.7 M Global Challenges Research Fund (GCRF) grant provided by the UK Research and Innovation’s Science and Technology Facilities Council (STFC), with the aim of improving researchers’ access to Diamond. The grant’s remit was to fund research posts focusing on two research areas crucial to African sustainable development: energy materials and structural biology. The aim was to align the project with key United Nations Sustainable Development Goals for health (SDG 3), energy (SDG 7), climate (SDG 13), and life-long learning (SDG 4), amongst others. In this article, we report on highlights of the programme and what’s next on the horizon for START.	Mar 2022
I07-Surface & interface diffraction	Structure of strained low‐dimensional Sb by in situ surface X‐ray diffraction Philip J. Mousley , Christopher W. Burrows , Chris Nicklin , Gavin R. Bell Physica Status Solidi (b) DOI: 10.1002/pssb.202100432 Diamond Proposal Number(s): [13769] Open Access Show Abstract ▼ Abstract: Antimony ultra-thin films in tensile strain are grown on InAs(111)B substrates and studied in situ using surface X-ray diffraction. The detailed atomic structures of two highly crystalline Sb(0001) films are derived, with thicknesses of 19 and 4 bilayers. Features considered in structural modelling include interfacial intermixing, surface roughness, individual layer relaxations and rotational twin domains (RTDs). The 4-bilayer film shows significant structural relaxation in every layer, while both films include RTDs. The results are discussed in relation to the topological properties of low-dimensional Sb.	Jan 2022
I07-Surface & interface diffraction	In-situ observations of the growth mode of vacuum deposited α-sexithiophene Thomas L. Derrien , Andreas E. Lauritzen , Pascal Kaienburg , Josue F. M. Hardigree , Christopher Nicklin , Moritz K. Riede The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.0c00447 Diamond Proposal Number(s): [20426, 24871] Open Access Show Abstract ▼ Abstract: The real-time morphological evolution of vacuum deposited α-sexithiophene (α-6T) on a weakly interacting (glass) substrate at ambient temperature is reported. In-situ grazing incidence small angle X-ray scattering (GISAXS) enabled the observation of nanoscale aggregates while in-situ grazing incidence wide angle scattering (GIWAXS) allowed the study of the molecular-scale morphology. The in-situ GISAXS measurements revealed that the α-6T growth proceeds via a Stranski-Krastanov mode, whereby 2-4 complete monolayers are deposited followed by subsequent layers formed via island growth. In-situ GIWAXS also showed the evolution of the polymorph composition during the thin film growth. Initially the disordered β-phase and the low-temperature (LT) phase are deposited in nearly equal proportion until a thickness of 8 nm whereby the LT-phase begins to dominate until a final α-6T thickness of 50 nm where the scattering intensity of the LT-phase is more than double that of the β-phase. The change in polymorph composition coincided with an increase in the LT-phase d-spacing, indicating a lattice strain relief as the thin film moves from surface to bulk mediated growth. The GISAXS findings were confirmed through direct imaging using ex-situ atomic force microscopy (AFM) at various thicknesses revealing the existence of both initial monolayers and intermediate and final island morphologies. The findings reveal the real-time morphological evolution of α-6T across both the molecular scale and the nanoscale and highlight the role of strain in polymorph growth. Due to the importance of thin film microstructure in device performance, it is expected that these results will aid in the development of the structure-property relationships necessary to realise the full potential of organic electronics.	May 2020
I07-Surface & interface diffraction	Spin splitting and strain in epitaxial monolayer WSe2 on graphene H. Nakamura , A. Mohammed , Ph. Rosenzweig , K. Matsuda , K. Nowakowski , K. Küster , P. Wochner , S. Ibrahimkutty , U. Wedig , H. Hussain , J. Rawle , C. Nicklin , B. Stuhlhofer , G. Cristiani , G. Logvenov , H. Takagi , U. Starke Physical Review B 101 DOI: 10.1103/PhysRevB.101.165103 Diamond Proposal Number(s): [18887] Open Access Show Abstract ▼ Abstract: We present the electronic and structural properties of monolayer WSe 2 grown by pulsed-laser deposition on monolayer graphene (MLG) on SiC. The spin splitting in the WSe 2 valence band at ¯¯¯ K was Δ SO = 0.469 ± 0.008 eV, as determined by angle-resolved photoemission spectroscopy. Synchrotron-based grazing-incidence in-plane x-ray diffraction (XRD) revealed the in-plane lattice constant of monolayer WSe 2 to be a WSe 2 = 3.2757 ± 0.0008 Å. This indicates a lattice compression of − 0.19 % relative to bulk WSe 2 . By using the experimentally determined graphene lattice constant ( a MLG = 2.4575 ± 0.0007 Å), we found that a 3 × 3 unit cell of the slightly compressed WSe 2 is perfectly commensurate with a 4 × 4 graphene lattice with a mismatch below 0.03%, which could explain why the monolayer WSe 2 is compressed on MLG. From XRD and first-principles calculations, we conclude that the observed size of strain will affect Δ SO only on the order of a few meV. In addition, angle-resolved, ultraviolet, and x-ray photoelectron spectroscopies shed light on the band alignment between WSe 2 and MLG/SiC and indicate electron transfer from graphene to the WSe 2 monolayer. As further revealed by atomic force microscopy, the WSe 2 island size depends on the number of carbon layers on top of the SiC substrate. This suggests that the epitaxy of WSe 2 favors the weak van der Waals interactions with graphene, while it is perturbed by the influence of the SiC substrate and its carbon buffer layer.	Apr 2020
I07-Surface & interface diffraction	In-situ investigation of crystallization and structural evolution of a metallic glass in three dimensions at nano-scale Bo Chen , Jiecheng Diao , Qiang Luo , Jonathan Rawle , Xianping Liu , Chris Nicklin , Jun Shen , Ian Robinson Materials & Design DOI: 10.1016/j.matdes.2020.108551 Diamond Proposal Number(s): [17445, 14918] Open Access Show Abstract ▼ Abstract: The crystallization behaviour of metallic glasses (MGs) has been investigated since the discovery of these important functional materials in order to optimize their synthesis procedures and improve their performances. Methods including powder X-ray diffraction and transmission electron microscopy are usually combined to characterize the crystalline structure in these “amorphous” materials. Until now, these methods, however, have failed to show the crystallization of individual crystals in three dimensions. In this work, in-situ Bragg coherent X-ray diffraction imaging (BCDI) reveals the growth and the strain variation of individual crystals in the Fe-based MGs during annealing. There is preferential growth along the surface of the MG sample particles during the crystal formation and fractal structure formation around the developing crystal surfaces; there is also strain relaxation happening from the inner parts to the surfaces of the developing crystals while cooling. The work leads to propose that during the crystallization of Fe-based MGs, the growth of the individual crystals follows a two-step procedure; and at higher temperature after the first crystallization period of the Fe-based MGs, the crystallization of α-Fe could be a competitive process between the growth of α-Fe crystals and the erosion from other elements.	Feb 2020
I07-Surface & interface diffraction	Dye nanoaggregate structures in MK-2, N3, and N749 dye…TiO2 interfaces that represent dye-sensitized solar cell working electrodes Ke Deng , Jacqueline M. Cole , Jonathan L. Rawle , Christopher Nicklin , Hao Chen , Angel Yanguas-Gil , Jeffrey W. Elam , Gavin B. G. Stenning Acs Applied Energy Materials DOI: 10.1021/acsaem.9b02002 Diamond Proposal Number(s): [15487] Show Abstract ▼ Abstract: The working electrode of a dye-sensitized solar cell (DSSC) consists of dye molecules adsorbed onto nanoparticles of a semiconductor such as TiO2. A reliable prediction of the DSSC photovoltaic performance of a given dye requires in-depth knowledge about the precise structure of the dye···TiO2 interface. X-ray reflectometry (XRR) and grazing-incidence small angle X-ray scattering (GISAXS) are herein employed to determine the dye···TiO2 interfacial structure and associated dye aggregation behavior of three high-performance DSSC dyes: an organic metal-free dye, MK-2, and the two archetypal ruthenium-based organometallic dyes, N3, and N749 (Black Dye). Results show that all three dyes form nanoaggregates in dye···TiO2 interfaces. We determine the dye nanoaggregate separations, sizes, distribution densities and the extent of short-range order within each dye self-assembly in the longitudinal and lateral directions. Dye···TiO2 composites fabricated using dye solutions of varying concentrations are analyzed. We find that nanoaggregates of the three dyes are separated by several hundred nanometers (158-203 nm) in dye···TiO2 interfaces that have been fabricated using concentrated dye solutions (0.5 mM or 1.0 mM). MK-2 and N749 dyes also display smaller inter-particle separations. Dye nanoparticle diameters are of the order of 156-198 nm, sizes that are comparable to the largest inter-particle separations. Thus, no extraneous dye particles can be fitted into gaps between particles, so the dye self-assembly is saturated. Self-assemblies of all three dyes exhibit both lateral and longitudinal short-range order; N3 displays a particularly short coherence length along the TiO2 surface, with extensive structured disorder along the longitudinal direction. The operation of DSSC working electrodes would therefore seem to be dependent on a dye self-assembly that may exhibit several levels of structural granularity and dye aggregation effects.	Dec 2019
I07-Surface & interface diffraction	Water-induced reversal of the TiO2 (011)-(2x1) surface reconstruction: observed with in situ surface X-ray diffraction Hadeel Hussain , Mahmoud H. M. Ahmed , Xavier Torrelles , David Grinter , Gregory Cabailh , Oier Bikondoa , Christopher Nicklin , Ulrich Aschauer , Robert Lindsay , Geoff Thornton The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.9b04383 Diamond Proposal Number(s): [8952] Open Access Show Abstract ▼ Abstract: The (011) termination of rutile TiO2 is reported to be particularly effective for photocatalysis. Here the structure of the interface formed between this substrate and water is revealed using surface X-ray diffraction. While the TiO2(011) surface exhibits a (2x1) reconstruction in ultra-high vacuum, this is lifted in the presence of a multilayer of water at room temperature. This change is driven by the formation of Ti-OH at the interface, which has a bond distance of 1.93 ± 0.02 Å. The experimental solution is in good agreement with density functional theory and first principles molecular dynamics calculations. These results point to the important differences that can arise between the structure of oxide surfaces in ultra-high vacuum and technical environments and will ultimately lead to an atomistic understanding of the photocatalytic process of water splitting on TiO2 surfaces.	May 2019
I07-Surface & interface diffraction	Structure of a superhydrophilic surface: wet chemically prepared rutile-TiO2(110)(1×1) Jon P. W. Treacy , Hadeel Hussain , Xavier Torrelles , Gregory Cabailh , Oier Bikondoa , Christopher Nicklin , Geoff Thornton , Robert Lindsay The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.9b00245 Open Access Show Abstract ▼ Abstract: Surface X-ray diffraction (SXRD) has been employed to quantitatively determine the geometric structure of an X-ray-induced superhydrophilic rutile-TiO2(110)(1×1) surface. A scatterer, assumed to be oxygen, is found at a distance of 1.90 ± 0.02 Å above the fivefold co-ordinated surface Ti atom, indicating surface hydroxylation. Two more oxygen atoms, situated further from the substrate, are also included to achieve the optimal agreement between experimental and simulated diffraction data. It is concluded that these latter scatterers are from water molecules, surface localised through hydrogen bonding. Comparing this interfacial structure with previous studies suggests that the superhydophilicity of titania is most likely to be a result of the depletion of surface carbon contamination, coupled with extensive surface hydroxylation.	Feb 2019

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