A5011095418- Molecular Junctions and Nanostructures
- Surface and Thin Film Phenomena
- Force Microscopy Techniques and Applications
- Surface Chemistry and Catalysis
- Graphene research and applications
- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Machine Learning in Materials Science
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Topological Materials and Phenomena
- Fullerene Chemistry and Applications
- Advanced Chemical Physics Studies
- Block Copolymer Self-Assembly
- Mechanical and Optical Resonators
- Advanced Materials Characterization Techniques
- Electron and X-Ray Spectroscopy Techniques
- 2D Materials and Applications
- Rare-earth and actinide compounds
- Spectroscopy and Quantum Chemical Studies
- Quantum and electron transport phenomena
- Superconductivity in MgB2 and Alloys
- Diamond and Carbon-based Materials Research
- Nanofabrication and Lithography Techniques
- Luminescence and Fluorescent Materials
University of British Columbia
2013-2024
Moffitt Cancer Center
2022
Vancouver Biotech (Canada)
2016
McGill University
2004-2010
University of California, Berkeley
2009
University of Cambridge
2007
Addenbrooke's Hospital
2007
Dalhousie University
2002-2003
Federal Reserve Bank of Philadelphia
2002
Concordance with growth hormone (GH) therapy in 75 children was objectively assessed using data on GP prescriptions over 12 months. 23% missed >2 injections/week. Lower concordance associated longer duration GH (p<0.005), lack of choice delivery device (p<0.005) and short prescription durations predicted lower height velocities (p<0.05).
Strain-induced Landau levels in wafer-scale graphene at room temperature are studied using momentum-resolved spectroscopy.
Submonolayer coverages of the molecule 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) deposited on NaCl(001) surfaces were imaged with high resolution noncontact-atomic force microscopy. Two island types observed: monolayer islands a p3x3 epitaxy at low coverage and mixture these bulklike crystallites higher coverage. The transition between pure mixed occurs approximately 0.85 ML, corresponding to complete layer. Calculations show be incompatible multilayer crystal PTCDA....
The superconducting compound, LiFeAs, is studied by scanning tunneling microscopy and spectroscopy. A gap map of the unreconstructed surface indicates a high degree homogeneity in this system. Spectra at 2 K show two nodeless gaps with $\Delta_1=5.3\pm0.1$ meV $\Delta_2=2.5\pm0.2$ meV. close as temperature increased to bulk $T_c$ indicating that accurately represents bulk. dip-hump structure observed below an energy scale consistent magnetic resonance recently reported inelastic neutron scattering.
Noncontact atomic force microscopy has been applied to the prototypical molecule-insulator system ${\mathrm{C}}_{60}$ on KBr study nucleation and submonolayer growth. Overview images reveal an island growth mode with unusual branching structures. Simultaneous molecular resolution surfaces, respectively, was obtained revealing a coincident $8\ifmmode\times\else\texttimes\fi{}3$ superstructure. Also, $21\ifmmode\pm\else\textpm\fi{}3\text{ }\text{ }\mathrm{p}\mathrm{m}$ apparent height...
Recent attention given to the growth and morphology of organic thin films with regard electronics has led observation dewetting (a transition from layer(s) islands) molecular deposits in many these systems. Dewetting is a much studied phenomenon formation polymer liquid films, but its 'small' molecules typical requires additional consideration structure interface between film substrate. This review covers some key concepts related growth. In particular, origins different modes thickness...
Semiconducting polymer dots (Pdots) have emerged as versatile probes for bioanalysis and imaging at the single-particle level. Despite their utility in multiplexed analysis, deep blue Pdots remain rare due to need high-energy excitation sensitivity photobleaching. Here, we describe design of fluorophores using structural constraints improve resistance photobleaching, two-photon absorption cross sections, fluorescence quantum yields hexamethylazatriangulene motif. Scanning tunneling...
Defects in LiFeAs are studied by scanning tunneling microscopy (STM) and spectroscopy (STS). Topographic images of the five predominant defects allow identification their position within lattice. The most commonly observed defect is associated with an Fe site does not break local lattice symmetry, exhibiting a bound state near edge smaller gap this multi-gap superconductor. Three other common defects, including one also on site, to symmetry pair-breaking indicated clear in-gap states,...
Abstract Organic semiconductor devices rely on the movement of charge at and near interfaces, making an understanding energy level alignment these boundaries essential element optimizing materials for electronic optoelectronic applications. Here we employ low temperature scanning tunneling microscopy spectroscopy to investigate a model system: two-dimensional nanostructures prototypical organic semiconductor, PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) adsorbed NaCl (2 ML)/Ag(111)....
Quasiparticle interference (QPI), by means of scanning tunneling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and multiorbital tight-binding calculations, is used to investigate the band structure superconducting order parameter LiFeAs. Using this combination techniques we identify intraband interband scattering vectors between hole ($h$) electron ($e$) bands in QPI maps. Discrepancies dispersions inferred from previous ARPES STM/STS are reconciled...
Materials exhibiting thermally activated delayed fluorescence (TADF) are now key components of some the most advanced organic light-emitting diodes, photocatalysts, and bioimaging probes. Designing a TADF emitter requires precise understanding its frontier molecular orbitals (FMOs), yet rarely these visualized experimentally. Here, we use scanning tunneling microscopy on Ag(111) to probe electronic structures high-performance materials with different orbital landscapes based s-triazine...
There has been increasing focus on the use of Kelvin probe force microscopy (KPFM) for determination local electronic structure in recent years, especially systems where other methods, such as scanning tunnelling microscopy/spectroscopy, may be intractable. We have examined three methods determining apparent contact potential difference (CPD): frequency modulation KPFM (FM-KPFM), amplitude (AM-KPFM), and shift–bias spectroscopy, a test system 3,4,9,10-perylene tetracarboxylic dianhydride...
Abstract Coordination chemistry relies on harnessing active metal sites within organic matrices. Polynuclear complexes—where ligands bind to several atoms—are relevant due their electronic/magnetic properties and potential for functional reactivity pathways. However, synthesis remains challenging; few geometries configurations have been achieved. Here, we synthesise—via supramolecular a noble surface—one-dimensional metal-organic nanostructures composed of terpyridine (tpy)-based molecules...
Submonolayer coverages of ${\mathrm{C}}_{60}$ deposited on KBr and NaCl are characterized by noncontact atomic force microscopy. Island shapes described both qualitatively quantitatively their dependence growth parameters substrate is discussed. At room temperature, compact branched island morphologies observed to coexist. An analysis the areas shows a distinct transition from morphology with increasing area. High-resolution imaging reveals differing coincident epitaxy at steps open...
Nanometer-scale rectangular pits in an insulating surface are used to template the growth of gold and PTCDA, a planar aromatic molecule (see image). The potential this approach for constructing molecular electronic device under controlled conditions ultrahigh vacuum is discussed.
Nanometre-scale 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) crystallites were produced by trapping the molecules inside monolayer-deep rectangular pits on an alkali halide surface. Noncontact atomic force microscopy was used to measure crystallite dimensions and lattice structure with molecular resolution. The molecule–substrate mismatch island heights, typically three four PTCDA layers, indicate a stress in first two layers. One- two-layer only observed side lengths smaller than 10 nm.
High-resolution Fourier transform scanning tunneling spectroscopy (FT-STS) is used to study many-body effects on the surface state of Ag(111). Our results reveal a kink in otherwise parabolic band dispersion electrons and an increase quasiparticle lifetime near Fermi energy Ef. The experimental data are accurately modeled with T-matrix formalism for scattering from single impurity, assuming that dressed by electron-electron electron-phonon interactions. We confirm latter as interaction...
Abstract Spin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by common appearance of distinct resonance spin susceptibility across cuprates, iron-based superconductors and many heavy fermion materials. The information we have about comes almost exclusively from neutron scattering. Here demonstrate that using low-temperature scanning tunnelling microscopy spectroscopy can characterize real space. We show inelastic leads to...
Deposition of submonolayer coverages 3,4,9,10-perylenetetracarboxylic diimide onto NaCl(001) results in the bimodal growth coexisting square and needle-shaped islands. The epitaxy each island type was determined from molecular atomic resolution noncontact force microscopy images. Postdeposition, needle islands grow while disappear completely within days. This is characterized as a dewetting transition, dynamics which has been described empirically fit to monomolecular model, model typically...
Tuning the electronic properties of graphene by adatom deposition unavoidably introduces disorder into system, which directly affects single-particle excitations and electrodynamics. Using angle-resolved photoemission spectroscopy (ARPES) we trace evolution in thallium probe its effect on structure. We show that signatures quasiparticle scattering spectral function can be used to identify adatoms, although charged, as efficient short-range centers. Employing a self-energy model for...
L. C. Martin, S. A. Burke and E. G. Knowles, Trans. Faraday Soc., 1935, 31, 495 DOI: 10.1039/TF9353100495
Non-contact atomic force microscopy (NC-AFM) was used to study thin films of C60 on Au(111). After observing the Au(111) reconstruction, 2–3 monolayers were deposited onto Au surface. The close-packed surface imaged by NC-AFM with molecular resolution. Enhanced corrugation and a stretching lattice observed at step edges. Based calculation required displace an edge molecule, it is proposed that effects are result tip-induced displacements molecules. While imaging small clusters C60, some...
Methods of tailoring molecular thin film morphology and maturation rate were investigated by noncontact atomic force microscopy. Submonolayer coverages 3,4,9,10-perylenetetracarboxylic diimide deposited on alkali-halides form films needle-shaped islands, undergo a dewetting transition when NaCl. The resulting island surface distribution, size, shape, may be varied changing growth conditions such as temperature templating the substrate with single layer deep pits or depositing gold...