A5081413879- X-ray Diffraction in Crystallography
- Quasicrystal Structures and Properties
- Crystallography and Radiation Phenomena
- Advanced X-ray Imaging Techniques
- Semiconductor Quantum Structures and Devices
- X-ray Spectroscopy and Fluorescence Analysis
- High-pressure geophysics and materials
- Semiconductor materials and interfaces
- Topological Materials and Phenomena
- Ion-surface interactions and analysis
- GaN-based semiconductor devices and materials
- Electron and X-Ray Spectroscopy Techniques
- Silicon Nanostructures and Photoluminescence
- Crystallization and Solubility Studies
- Mineralogy and Gemology Studies
- Theoretical and Computational Physics
- Semiconductor materials and devices
- Surface and Thin Film Phenomena
- Diamond and Carbon-based Materials Research
- Advanced Condensed Matter Physics
- Advanced ceramic materials synthesis
- Crystallography and molecular interactions
- Enzyme Structure and Function
- Magnetism in coordination complexes
- Thermodynamic and Structural Properties of Metals and Alloys
University of Guelph
2015-2025
Canadian Light Source (Canada)
2023
University of Waterloo
2018
University of Oxford
2011
Universities UK
2011
Brazilian Synchrotron Light Laboratory
2001-2009
Universidade Estadual de Campinas (UNICAMP)
2009
Ames National Laboratory
1992-2002
Iowa State University
1992-2002
Computational Physics (United States)
2002
The structure factor $S(Q)$ of high purity amorphous Si membranes prepared by ion implantation was measured over an extended $Q$ range ( $0.03--55{\AA{}}^{\ensuremath{-}1}$). Calculation the first neighbor shell coordination ${C}_{1}$) as a function maximum indicates that measurement out to at least $40{\AA{}}^{\ensuremath{-}1}$ is required reliably determine radial distribution (RDF). A $2%$ change in ${C}_{1}$ and subtle changes rest RDF were observed upon annealing, consistent with point...
The controlled synthesis of PbSe nanocrystal quantum dots with narrow size distributions was achieved through phase decomposition the solid solution in a phosphate glass host. Structural characterization by electron microscopy and x-ray diffraction shows that have mean diameters between 2 15 nm. exciton Bohr radius aB=46 nm PbSe, so these provide unusual perhaps unique access to regime strong confinement. optical absorption spectra are compared predictions theoretical treatment electronic...
Medium and high-energy x-ray diffraction has been used to study the atomic structure of pure amorphous Si prepared by MeV implantation into crystalline silicon. Both as-implanted annealed samples were studied. The inelastically scattered x rays removed fitting energy spectrum for rays. scattering factor silicon, previously known reliably up 20 ${\mathrm{\AA{}}}^{\mathrm{\ensuremath{-}}1}$, extended 55 ${\mathrm{\AA{}}}^{\mathrm{\ensuremath{-}}1}$. radial distribution function Si, before...
Despite global efforts to reduce carbon dioxide (CO2) emissions, continued industrialization threatens exacerbate climate change. This work investigates methods capture CO2, with a focus on the SIFSIX-3-Ni metal–organic framework (MOF) as direct air (DAC) sorbent. exhibits promising CO2 adsorption properties but suffers from degradation processes under accelerated aging, which are akin column regeneration conditions. Herein, we have grown largest single crystals date, facilitating crystal...
Three-dimensional composition maps of nominally pure Ge domes grown on Si(001) at 600 degrees C were obtained from grazing incidence anomalous x-ray scattering data the K edge. The analyzed in terms a stack layers with laterally varying concentration. results demonstrated that contained Si-rich core covered by Ge-rich shell and independently supported selective etch experiments. profile resulted substrate Si alloying into during growth to partially relax stress under domes.
The diffuse scattering located close to Bragg reflections has been measured on a single grain of the AlPdMn icosahedral phase using elastic neutron scattering. This is mainly due phason disorder. intensity distribution and anisotropic shape can be reproduced in framework theory quasicrystals only two constants whose ratio found equal $\ensuremath{-}0.5$.
A new beamline, fully dedicated to X-ray powder diffraction (XPD) measurements, has been installed after the exit port B of bending magnet D10 at Brazilian Synchrotron Light Laboratory (LNLS) and commissioned. The technical characteristics beamline are described some performance indicators listed, such as incoming photon flux angular/energy resolutions obtainable under typical experimental conditions. results a Rietveld refinement for standard sample Y2O3 using high-resolution data shown....
Hemozoin (Hz) is a heme crystal produced upon the digestion of hemoglobin (Hb) by blood‐feeding organisms as main mechanism disposal. The structure Hz consists dimers bound reciprocal iron–carboxylate interactions and stabilized hydrogen bonds. We have recently described crystals in blood fluke, Schistosoma mansoni, kissing bug, Rhodnius prolixus . Here, we characterized structures morphologies from those two compared them to synthetic β‐hematin (βH). Synchrotron radiation X‐ray powder...
Core/shell and core/shell/shell particles comprised of the Prussian blue analogues K(j)Ni(k)[Cr(CN)(6)](l)·nH(2)O (A) Rb(a)Co(b)[Fe(CN)(6)](c)·mH(2)O (B) have been prepared for purpose studying persistent photoinduced magnetization in heterostructures. Synthetic procedures refined to allow controlled growth relatively thick (50-100 nm) consecutive layers while minimizing mixing materials at interfaces. Through changes order which two components are added, with AB, ABA, BA, BAB sequences...
A new diffraction beamline for materials science has been built at the Canadian Light Source synchrotron. The X-ray source is an in-vacuum wiggler with a 2.5 T peak magnetic field 5.2 mm gap. optical configuration includes toroidal mirror, single side-bounce Bragg monochromator, and cylindrical producing sub-150 µm vertical × 500 horizontal focused beam photon energy range of 7–22 keV flux 10 12 photons per second sample position. Three endstations are currently open to general users,...
Ruthenium-based nanomaterials have seen increased interest as an alternative to platinum electrocatalysts for the hydrogen evolution reaction (HER). In this study, ruthenium nanoparticles supported on a graphene-based composite consisting of expanded graphite and reduced graphene oxide were successfully prepared by using one-step thermal method. The nanocomposite was optimized alkaline HER performance varying content annealing temperature, exhibiting overpotential 54 mV achieve 10 mA cm–2,...
High real-space resolution atomic pair distribution functions PDFs from the alloy series $\mathrm{Ga}{}_{1\ensuremath{-}x}{ln}_{x}\mathrm{As}$ have been obtained using high-energy x-ray diffraction. The first peak in PDF is resolved as a doublet due to presence of two nearest neighbor bond lengths, Ga-As and In-As, previously observed absorption fine structure. widths nearest, higher, peaks are analyzed by separating broadening static atom displacements thermal motion. width 5 times larger...
We present direct evidence of dynamical diffraction x rays from a quasicrystal. High-resolution x-ray-diffraction measurements the Al-Pd-Mn face-centered icosahedral quasicrystal were performed, revealing mosaic full width at half maximum less than 0.001\ifmmode^\circ\else\textdegree\fi{}. In second experiment, anomalous transmission (the Borrmann effect) was observed. These show that nearly perfect quasicrystals may be grown to centimeter-size dimensions allowing x-ray techniques based upon...
Using real-time x-ray scattering to measure the surface morphology of Au(111) during sputter erosion with 500 eV ${\mathrm{Ar}}^{+}$ ions, we observe three distinct regimes: three-dimensional rough at 20-- $60\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, quasi-layer-by-layer removal 120-- $220\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, and step retraction above $270\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. Sputtering $60\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ leads pattern...
The growth of strained epitaxial self assembled nanocrystals is comprised a variety kinetic and thermodynamic factors that determine their morphology size. Some the significant to stability are strain interdiffusion. Here we directly measure gradient composition in Ge grown on Si(001) using anomalous x-ray scattering. By combining our results, where relate strain, interdiffusion, shape with atomic force microscopy measurements, have been able complete configuration these islands. We show...
The design, performance, and capabilities of the High Energy beamline at Brockhouse Sector Canadian Light Source are described. uses a single bent silicon wafer as side-bounce Laue monochromator, using (111), (422), or (533) hkl reflections to access energies ranging from 25 90 keV. cryogenically cooled crystal serves only optical element in providing simple, convenient, reliable configuration. bending provides vertical focus small 20 µm. flux ranges 1 × 10 13 photons s −1 , depending on...
The Brockhouse sector of the Canadian Light Source is a suite three hard X-ray beamlines dedicated to diffraction and scattering for materials science. opened general users during 2020-2021. Multiple experimental stations enable several techniques, including: synchrotron high resolution powder (XRD), energy XRD, thin film characterization, total pair distribution function (PDF) experiments, small angle (SAXS), in-situ experiments with multiple environments. chemistry community eagerly seized...
High real-space-resolution atomic pair distribution functions of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ $(x=0.12,$ 0.25, and 0.33) have been measured using high-energy x-ray powder diffraction to study the size shape ${\mathrm{MnO}}_{6}$ octahedron as a function temperature doping. In paramagnetic insulating phase we find evidence for three distinct bond lengths which ascribe ${\mathrm{Mn}}^{4+}\ensuremath{-}\mathrm{O},$...
Nearest- and higher-neighbor distances as well bond length distributions (static thermal) of the ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ $(0<~x<~1)$ semiconductor alloys have been obtained from high-real-space resolution atomic pair distribution functions. Using this structural information, we modeled local displacements in alloys. From a supercell model based on Kirkwood potential, three-dimensional As (In,Ga) ensemble average probability distributions. These clearly...
Angular-resolved photoelectron spectra from the fivefold surface of single-grain icosahedral ${\mathrm{Al}}_{70}$${\mathrm{Pd}}_{21.5}$${\mathrm{Mn}}_{8.5}$ exhibit a quasiperiodic dispersion 300 meV at 2.3 eV binding energy. Low energy electron diffraction studies confirm quasicrystalline order surface. A distinct pseudogap feature is observed with density states near Fermi level decreasing as square-root power law.
An open (closed) system, in which matter is (not) exchanged through surface diffusion, was realized via growth kinetics. Epitaxially grown Si-Ge:Si (001) islands were annealed different environments affecting the diffusivity of Si adatoms selectively. The evolution driving forces for intermixing while approaching equilibrium inferred from Synchrotron x-ray measurements composition and strain. For due to inflow wetting layer (reservoir) caused a decrease Ge content, leading lowering elastic...
Acetic and formic acid impart a high acidity on pyrolysis bio-oil (obtained by fast of ligno-cellulosic biomass), which is one the factors preventing its direct use as fuel. At temperatures ≥ 330 °C, Red Mud, waste byproduct aluminum industry produced at >70 million tons p.a., good catalyst for thermal decomposition these acids. Formic can serve an internal source hydrogen through formation synthesis gas water shift reaction. The C6−C10 hydrocarbons in nonpolar phase resulting product...