16 results on '"Nadav Avidor"'
Search Results
2. PIGLE - Particles Interacting in Generalized Langevin Equation simulator.
- Author
-
Nadav Avidor, Peter S. M. Townsend, D. J. Ward, A. P. Jardine, John Ellis, and William Allison
- Published
- 2019
- Full Text
- View/download PDF
3. Evolution of ordered nanoporous phases during h-BN growth: controlling the route from gas-phase precursor to 2D material by
- Author
-
Adrian, Ruckhofer, Marco, Sacchi, Anthony, Payne, Andrew P, Jardine, Wolfgang E, Ernst, Nadav, Avidor, and Anton, Tamtögl
- Abstract
Large-area single-crystal monolayers of two-dimensional (2D) materials such as graphene and hexagonal boron nitride (h-BN) can be grown by chemical vapour deposition (CVD). However, the high temperatures and fast timescales at which the conversion from a gas-phase precursor to the 2D material appears, make it extremely challenging to simultaneously follow the atomic arrangements. We utilise helium atom scattering to discover and control the growth of novel 2D h-BN nanoporous phases during the CVD process. We find that prior to the formation of h-BN from the gas-phase precursor, a metastable (3 × 3) structure is formed, and that excess deposition on the resulting 2D h-BN leads to the emergence of a (3 × 4) structure. We illustrate that these nanoporous structures are produced by partial dehydrogenation and polymerisation of the borazine precursor upon adsorption. These steps are largely unexplored during the synthesis of 2D materials and we unveil the rich phases during CVD growth. Our results provide significant foundations for 2D materials engineering in CVD, by adjusting or carefully controlling the growth conditions and thus exploiting these intermediate structures for the synthesis of covalent self-assembled 2D networks.
- Published
- 2022
4. Evolution of ordered nanoporous phases during h-BN growth: Controlling the route from gas-phase precursor to 2D material by $\textit{in-situ}$ monitoring
- Author
-
Adrian Ruckhofer, Marco Sacchi, Anthony Payne, Andrew P. Jardine, Wolfgang E. Ernst, Nadav Avidor, and Anton Tamtögl
- Subjects
Chemical Physics (physics.chem-ph) ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Physics - Chemical Physics ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Materials Science - Abstract
Large-area single-crystal monolayers of two-dimensional (2D) materials such as graphene and hexagonal boron nitride (h-BN) can be grown by chemical vapour deposition (CVD). However, the high temperatures and fast timescales at which the conversion from a gas-phase precursor to the 2D material appear, make it extremely challenging to simultaneously follow the atomic arrangements. We utilise helium atom scattering to discover and control the growth of novel 2D h-BN nanoporous phases during the CVD process. We find that prior to the formation of h-BN from the gas-phase precursor, a metastable $(3\times3)$ structure is formed, and that excess deposition on the resulting 2D h-BN leads to the emergence of a $(3\times4)$ structure. We illustrate that these nanoporous structures are produced by partial dehydrogenation and polymerisation of the borazine precursor upon adsorption. These steps are largely unexplored during the synthesis of 2D materials and we unveil the rich phases during CVD growth. Our results provide significant foundations for 2D materials engineering in CVD, by adjusting or carefully controlling the growth conditions and thus exploiting these intermediate structures for the synthesis of covalent self-assembled 2D networks.
- Published
- 2022
5. Nanoscopic diffusion of water on a topological insulator
- Author
-
Peter S. M. Townsend, John Ellis, William Allison, Anton Tamtögl, Irene Calvo-Almazán, Martin Bremholm, Philip Hofmann, Marco Sacchi, Nadav Avidor, Tamtögl, Anton [0000-0001-9590-6224], Sacchi, Marco [0000-0003-2904-2506], Avidor, Nadav [0000-0002-3928-2493], Bremholm, Martin [0000-0003-3634-7412], and Apollo - University of Cambridge Repository
- Subjects
Reaction kinetics and dynamics ,Science ,Jump diffusion ,General Physics and Astronomy ,02 engineering and technology ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,0103 physical sciences ,Diffusion (business) ,010306 general physics ,lcsh:Science ,Nanoscopic scale ,Brownian motion ,Physics::Atmospheric and Oceanic Physics ,Multidisciplinary ,34 Chemical Sciences ,Dynamics (mechanics) ,General Chemistry ,021001 nanoscience & nanotechnology ,Surface spectroscopy ,Chemical physics ,Topological insulator ,Nanotribology ,3406 Physical Chemistry ,Density functional theory ,Condensed Matter::Strongly Correlated Electrons ,lcsh:Q ,0210 nano-technology ,51 Physical Sciences - Abstract
The microscopic motion of water is a central question, but gaining experimental information about the interfacial dynamics of water in fields such as catalysis, biophysics and nanotribology is challenging due to its ultrafast motion, and the complex interplay of inter-molecular and molecule-surface interactions. Here we present an experimental and computational study of the nanoscale-nanosecond motion of water at the surface of a topological insulator (TI), Bi\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${}_{2}$$\end{document}2Te\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${}_{3}$$\end{document}3. Understanding the chemistry and motion of molecules on TI surfaces, while considered a key to design and manufacturing for future applications, has hitherto been hardly addressed experimentally. By combining helium spin-echo spectroscopy and density functional theory calculations, we are able to obtain a general insight into the diffusion of water on Bi\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${}_{2}$$\end{document}2Te\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${}_{3}$$\end{document}3. Instead of Brownian motion, we find an activated jump diffusion mechanism. Signatures of correlated motion suggest unusual repulsive interactions between the water molecules. From the lineshape broadening we determine the diffusion coefficient, the diffusion energy and the pre-exponential factor., Water molecular motion on surfaces underpins a range of phenomena in nature. The authors resolve the nanoscale-nanosecond motion of water at a topological insulator’s surface by helium spin-echo spectroscopy and computations, reporting hopping among sites and repulsion between water molecules.
- Published
- 2020
6. Ultrafast Diffusion at the Onset of Growth: O/Ru(0001)
- Author
-
Jack Kelsall, John Ellis, Nadav Avidor, Peter S. M. Townsend, and Andrew Jardine
- Subjects
Crystallography ,Materials science ,Phase (matter) ,Diffusion ,0103 physical sciences ,Atomic oxygen ,General Physics and Astronomy ,Substrate (electronics) ,Activation energy ,010306 general physics ,01 natural sciences ,Ultrashort pulse - Abstract
Nanoscopic clustering in a 2D disordered phase is observed for oxygen on Ru(0001) at low coverages and high temperatures. We study the coexistence of quasistatic clusters (with a characteristic length of $\ensuremath{\sim}9\text{ }\text{ }\AA{}$) and highly mobile atomic oxygen which diffuses between the energy-inequivalent, threefold hollow sites of the substrate. We determine a surprisingly low activation energy for diffusion of $385\ifmmode\pm\else\textpm\fi{}20\text{ }\text{ }\mathrm{meV}$. The minimum of the $\mathrm{O}\ensuremath{-}\mathrm{O}$ interadsorbate potential appears to be at lower separations than previously reported.
- Published
- 2021
7. Material properties particularly suited to be measured with helium scattering: selected examples from 2D materials, van der Waals heterostructures, glassy materials, catalytic substrates, topological insulators and superconducting radio frequency materials
- Author
-
Justin W. Wells, Wolfgang Ernst, Bodil Holst, Andrew Jardine, Nadav Avidor, Steven J. Sibener, Kim Lefmann, Gil Alexandrowicz, William Allison, Giorgio Benedek, Salvador Miret Artés, Daniel Farías, Gianangelo Bracco, J. R. Manson, Roberto Marquardt, Anton Tamtögl, UAM. Departamento de Física de la Materia Condensada, Holst, B, Alexandrowicz, G, Avidor, N, Benedek, G, Bracco, N, Ernst, W, Farías, D, Jardine, A, Manson, J, Marquardt, R, Miret Artés, S, Tamtögl, A, Wells, J, and Allison, W
- Subjects
DYNAMICS ,GRAPHENE ,ATOM-SURFACE SCATTERING ,Inelastic-Scattering ,Materials science ,Spin-Echo ,General Physics and Astronomy ,chemistry.chemical_element ,Context (language use) ,02 engineering and technology ,01 natural sciences ,INELASTIC-SCATTERING ,Molecular-Beams ,0103 physical sciences ,Atom ,Physics::Atomic and Molecular Clusters ,Physics::Atomic Physics ,Physical and Theoretical Chemistry ,010306 general physics ,Helium atom scattering ,TRANSITION-TEMPERATURE ,Helium ,ADSORPTION RESONANCES ,Surface diffusion ,Condensed matter physics ,Electronic Corrugation ,Scattering ,Superconducting radio frequency ,Física ,021001 nanoscience & nanotechnology ,Boson Peak ,Dynamics ,MOLECULAR-BEAMS ,chemistry ,Topological insulator ,ELECTRONIC CORRUGATION ,Transition-Temperature ,Helium atom scattering, Two-dimensional materials, van der Waals heterostructures, Glassy materials, Catalytic substrates, Topological insulators, Superconducting radio-frequency material ,Physics::Accelerator Physics ,BOSON PEAK ,SPIN-ECHO ,Graphene ,0210 nano-technology ,Atom-Surface Scattering ,Adsorption Resonances - Abstract
20 pags., 10 figs., 1 tab., Helium Atom Scattering (HAS) and Helium Spin-Echo scattering (HeSE), together helium scattering, are well established, but non-commercial surface science techniques. They are characterised by the beam inertness and very low beam energy (
- Published
- 2021
8. Alkali metal adsorption on metal surfaces: new insights from new tools
- Author
-
Alexander Spreinat, John Ellis, David J. Ward, Marco Sacchi, Louie Slocombe, Arjun Raghavan, Andrew Jardine, William Allison, Nadav Avidor, Ward, David [0000-0002-1587-7011], Avidor, Nadav [0000-0002-3928-2493], and Apollo - University of Cambridge Repository
- Subjects
Coupling constant ,Materials science ,34 Chemical Sciences ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Molecular dynamics ,3407 Theoretical and Computational Chemistry ,Adsorption ,chemistry ,0103 physical sciences ,Bravais lattice ,Density functional theory ,Physical and Theoretical Chemistry ,Diffusion (business) ,010306 general physics ,0210 nano-technology ,Spectroscopy ,51 Physical Sciences ,Helium - Abstract
The adsorption of sodium on Ru(0001) is studied using 3He spin-echo spectroscopy (HeSE), molecular dynamics simulations (MD) and density functional theory (DFT). In the multi-layer regime, an analysis of helium reflectivity, gives an electron-phonon coupling constant of λ = 0.64 ± 0.06. At sub-monolayer coverage, DFT calculations show that the preferred adsorption site changes from hollow site to top site as the supercell increases and the effective coverage, θ, is reduced from 0.25 to 0.0625 adsorbates per substrate atom. Energy barriers and adsorption geometries taken from DFT are used in molecular dynamics calculations to generate simulated data sets for comparison with measurements. We introduce a new Bayesian method of analysis that compares measurement and model directly, without assuming analytic lineshapes. The value of adsorbate-substrate energy exchange rate (friction) in the MD simulation is the sole variable parameter. Experimental data at a coverage θ = 0.028 compares well with the low-coverage DFT result, giving an effective activation barrier Eeff = 46 ± 4 meV with a friction γ = 0.3 ps-1. Better fits to the data can be achieved by including additional variable parameters, but in all cases, the mechanism of diffusion is predominantly on a Bravais lattice, suggesting a single adsorption site in the unit cell, despite the close packed geometry.
- Published
- 2020
9. Ultrafast Diffusion at the Onset of Growth: O/Ru(0001)
- Author
-
Jack, Kelsall, Peter S M, Townsend, John, Ellis, Andrew P, Jardine, and Nadav, Avidor
- Abstract
Nanoscopic clustering in a 2D disordered phase is observed for oxygen on Ru(0001) at low coverages and high temperatures. We study the coexistence of quasistatic clusters (with a characteristic length of ∼9 Å) and highly mobile atomic oxygen which diffuses between the energy-inequivalent, threefold hollow sites of the substrate. We determine a surprisingly low activation energy for diffusion of 385±20 meV. The minimum of the O-O interadsorbate potential appears to be at lower separations than previously reported.
- Published
- 2020
10. Probing surface motion above ambient temperature with helium spin-echo spectroscopy
- Author
-
Nadav Avidor
- Subjects
Surface (mathematics) ,Materials science ,chemistry ,Spin echo ,General Physics and Astronomy ,Motion (geometry) ,chemistry.chemical_element ,Atomic physics ,Spectroscopy ,Computer Science::Databases ,Helium - Abstract
Nadav Avidor explains how helium spin-echo spectroscopy can be used to probe high-temperature surface motion.
- Published
- 2021
11. Signatures of multiple jumps in surface diffusion on honeycomb surfaces
- Author
-
Nadav Avidor and Peter S. M. Townsend
- Subjects
Surface diffusion ,Surface (mathematics) ,Physics ,Jump diffusion ,02 engineering and technology ,Dissipation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Molecular dynamics ,Distribution (mathematics) ,0103 physical sciences ,Jump ,Diffusion (business) ,010306 general physics ,0210 nano-technology - Abstract
The jump distribution, a property of the motion of adsorbates on a corrugated surface, contains crucial information on adsorbate-substrate energy dissipation processes. To provide a means to study jump distributions in a honeycomb array of adsorption sites, we derive analytical expressions for the intermediate scattering function (ISF) describing jump diffusion taking into account jumps up to fourth-nearest neighbor in length. To enable testing the analytical expressions against experimental or simulated data, we develop a global fitting routine that can be applied to experimental or simulated ISFs to infer multiple jumps. We demonstrate the analysis method by studying the jump distribution arising from classical Langevin molecular dynamics simulations of two model systems, cyclopentadienyl (Cp) on Cu(111), and deuterium (D) on Pd(111). The simulations and analysis confirm that diffusion of Cp/Cu(111) at a surface temperature ${T}_{s}=135$ K takes place in a regime of predominantly single jumps. Classical simulations of D/Pd(111) at ${T}_{s}=350$ K, with a realistic Langevin friction, suggest that the diffusion of D/Pd(111) involves a high proportion of multiple jumps. The parameters that apply to D/Pd(111) are typical of the interaction of hydrogen atoms with close-packed transition metal surfaces, suggesting that long jumps are a general feature of the high temperature surface diffusion of hydrogen.
- Published
- 2019
12. Two-Dimensional Wetting of a Stepped Copper Surface
- Author
-
Gefen Corem, Chenfang Lin, Gil Alexandrowicz, Nadav Avidor, Andrew Hodgson, Oded Godsi, George R. Darling, Avidor, Nadav [0000-0002-3928-2493], and Apollo - University of Cambridge Repository
- Subjects
0306 Physical Chemistry (incl. Structural) ,Surface (mathematics) ,Materials science ,Pentamer ,Hydrogen bond ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Random hexamer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Copper ,0104 chemical sciences ,Crystallography ,Dipole ,chemistry ,Molecule ,Wetting ,0210 nano-technology - Abstract
Highly corrugated, stepped surfaces present regular 1D arrays of binding sites, creating a complex, heterogeneous environment to water. Rather than decorating the hydrophilic step sites to form 1D chains, water on stepped Cu(511) forms an extended 2D network that binds strongly to the steps but bridges across the intervening hydrophobic Cu(100) terraces. The hydrogen-bonded network contains pentamer, hexamer, and octomer water rings that leave a third of the stable Cu step sites unoccupied in order to bind water H down close to the step dipole and complete three hydrogen bonds per molecule.
- Published
- 2017
13. Electron-phonon coupling and surface Debye temperature of Bi2Te3 (111) from helium atom scattering
- Author
-
Nadav Avidor, William Allison, Martin Bremholm, Patrick Kraus, John Ellis, Philip Hofmann, Giorgio Benedek, Wolfgang Ernst, Bo B. Iversen, Ellen M. J. Hedegaard, Anton Tamtögl, and Marco Bianchi
- Subjects
Physics ,Scattering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Coupling (probability) ,01 natural sciences ,symbols.namesake ,Topological insulator ,0103 physical sciences ,symbols ,Debye function ,Atomic physics ,010306 general physics ,0210 nano-technology ,Helium atom scattering ,Debye model ,Debye length ,Morse potential - Abstract
We have studied the topological insulator Bi$_2$Te$_3$(111) by means of helium atom scattering. The average electron-phonon coupling $\lambda$ of Bi$_2$Te$_3$(111) is determined by adapting a recently developed quantum-theoretical derivation of the helium scattering probabilities to the case of degenerate semiconductors. Based on the Debye-Waller attenuation of the elastic diffraction peaks of Bi$_2$Te$_3$(111), measured at surface temperatures between $110~\mbox{K}$ and $355~\mbox{K}$, we find $\lambda$ to be in the range of $0.04-0.11$. This method allows to extract a correctly averaged $\lambda$ and to address the discrepancy between previous studies. The relatively modest value of $\lambda$ is not surprising even though some individual phonons may provide a larger electron-phonon interaction. Furthermore, the surface Debye temperature of Bi$_2$Te$_3$(111) is determined as ${\rm \Theta}_D = (81\pm6)~\mbox{K}$. The electronic surface corrugation was analysed based on close-coupling calculations. By using a corrugated Morse potential a peak-to-peak corrugation of 9% of the lattice constant is obtained.
- Published
- 2017
14. Note: A simple sample transfer alignment for ultra-high vacuum systems
- Author
-
EA Carter, Anton Tamtögl, Nadav Avidor, Andrew Jardine, William Allison, David J. Ward, Pepijn R. Kole, Ward, David [0000-0002-1587-7011], Avidor, Nadav [0000-0002-3928-2493], and Apollo - University of Cambridge Repository
- Subjects
business.product_category ,business.industry ,Computer science ,02 engineering and technology ,Processing ,021001 nanoscience & nanotechnology ,01 natural sciences ,Sample (graphics) ,Software ,Optics ,Transfer (computing) ,0103 physical sciences ,0801 Artificial Intelligence and Image Processing ,Vacuum chamber ,Transfer alignment ,010306 general physics ,0210 nano-technology ,business ,Adaptation (computer science) ,Instrumentation ,computer ,Computer hardware ,computer.programming_language ,Digital camera - Abstract
The alignment of ultra-high-vacuum sample transfer systems can be problematic when there is no direct line of sight to assist the user. We present the design of a simple and cheap system which greatly simplifies the alignment of sample transfer devices. Our method is based on the adaptation of a commercial digital camera which provides live views from within the vacuum chamber. The images of the camera are further processed using an image recognition and processing code which determines any misalignments and reports them to the user. Installation has proven to be extremely useful in order to align the sample with respect to the transfer mechanism. Furthermore, the alignment software can be easily adapted for other systems.
- Published
- 2016
15. A magnetically focused molecular beam of ortho-water
- Author
-
A. Bekkerman, Mitya Reznikov, Y. Meir, T. Kravchuk, P. Tichonov, Nadav Avidor, and Gil Alexandrowicz
- Subjects
Multidisciplinary ,Hydrogen ,Magnetic moment ,chemistry.chemical_element ,Antiparallel (biochemistry) ,Magnetic field ,Nuclear magnetic resonance ,chemistry ,Chemical physics ,Physics::Atomic and Molecular Clusters ,Molecule ,Physics::Chemical Physics ,Spin (physics) ,Molecular beam ,Beam (structure) - Abstract
Like dihydrogen, water exists as two spin isomers, ortho and para, with the nuclear magnetic moments of the hydrogen atoms either parallel or antiparallel. The ratio of the two spin isomers and their physical properties play an important role in a wide variety of research fields, ranging from astrophysics to nuclear magnetic resonance (NMR). Unlike ortho and para H(2), however, the two water isomers remain challenging to separate, and as a consequence, very little is currently known about their different physical properties. Here, we report the formation of a magnetically focused molecular beam of ortho-water. The beam we formed also had a particular spin projection. Thus, in the presence of holding magnetic fields, the water molecules are hyperpolarized, laying the foundation for ultrasensitive NMR experiments in the future.
- Published
- 2011
16. Highly Proton-Ordered Water Structures on Oxygen Precovered Ru{0001}
- Author
-
Gil Alexandrowicz, Nadav Avidor, T. Kravchuk, Holly Hedgeland, William Allison, Andrew Jardine, John Ellis, and Georg Held
- Subjects
Diffraction ,chemistry ,Proton ,Scattering ,Chemical physics ,Binding energy ,chemistry.chemical_element ,Molecule ,Nanotechnology ,Physical and Theoretical Chemistry ,Oxygen ,Helium ,Line (formation) - Abstract
We present helium scattering measurements of a water ad-layer grown on a O(2 × 1)/Ru(0001) surface. The adsorbed water layer results in a well ordered helium diffraction pattern with systematic extinctions of diffraction spots due to glide line symmetries. The data reflects a well-defined surface structure that maintains proton order even at surprisingly high temperatures of 140 K. The diffraction data we measure is consistent with a structure recently derived from STM measurements performed at 6 K. Comparison with recent DFT calculation is in partial agreement, suggesting that these calculations might be underestimating the contribution of relative water molecule orientations to the binding energy.
- Published
- 2011
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.