A5039544146- Surface and Thin Film Phenomena
- Magnetic properties of thin films
- Physics of Superconductivity and Magnetism
- Molecular Junctions and Nanostructures
- Semiconductor materials and interfaces
- Electronic and Structural Properties of Oxides
- Advanced Chemical Physics Studies
- Semiconductor materials and devices
- Graphene research and applications
- Semiconductor Quantum Structures and Devices
- 2D Materials and Applications
- Quantum and electron transport phenomena
- nanoparticles nucleation surface interactions
- Surface Chemistry and Catalysis
- Advanced Materials Characterization Techniques
- Force Microscopy Techniques and Applications
- Machine Learning in Materials Science
- Advanced Condensed Matter Physics
- Electrochemical sensors and biosensors
- Theoretical and Computational Physics
- Metallurgical and Alloy Processes
- Quantum, superfluid, helium dynamics
- Conducting polymers and applications
- Metal and Thin Film Mechanics
- Advanced Thermodynamics and Statistical Mechanics
University of Missouri
2023
Missouri College
2023
Lakehead University
2003-2020
Thunder Bay Regional Research Institute
2019
Pacific Northwest National Laboratory
1996-2003
Environmental Molecular Sciences Laboratory
1995-2003
Pennsylvania State University
1991-1994
University of Alberta
1870-1991
A combination of angle-resolved photoemission and scanning tunneling microscopy is used to explore the possibilities for tailoring electronic structure gold atom chains on silicon surfaces. It shown that interchain coupling band filling can be adjusted systematically by varying step spacing via tilt angle from Si(111). Planes with odd Miller indices are stabilized atoms. Metallic bands Fermi surfaces observed. These findings suggest atomic at stepped semiconductor substrates make a highly...
We report the synthesis of extended two-dimensional organic networks on Cu(111), Ag(111), Cu(110), and Ag(110) from thiophene-based molecules. A combination scanning tunnelling microscopy X-ray photoemission spectroscopy yields insight into reaction pathways single molecules towards formation organometallic polymeric structures via Ullmann dehalogenation C-C coupling. The thermal stability molecular is probed by annealing at elevated temperatures up to 500 °C. On Cu(111) only are formed,...
Scanning tunneling microscopy (STM) and point-probe electrical conductivity measurements of electrochemically protonated films the emeraldine-base form conducting polymer, polyaniline are reported. The varies spatially, dependent on size ( L M ≈ 200 to 300 angstroms) granular metallic regions which relate directly inhomogeneous micromorphology electrodeposited films. normalized at zero bias is observed increase with doping, indicating an in states Fermi level. STM electronic also show...
The $\mathrm{Si}(111)5\ifmmode\times\else\texttimes\fi{}2\text{\ensuremath{-}}\mathrm{Au}$ surface exhibits a chain structure with additional Si atoms on top of the chains. They dope chains to achieve optimum band filling, according recent local density calculations. Surprisingly, form half-filled, disordered $5\ifmmode\times\else\texttimes\fi{}4$ lattice fluid, not an ordered $5\ifmmode\times\else\texttimes\fi{}8$ lattice. From their autocorrelation function interatomic potential...
A semiconducting surface-state band on $\mathrm{Si}(111)\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}\ensuremath{-}\mathrm{Ag}$ is doped by adsorption of additional Ag and Au atoms. Very high levels doping can be achieved (0.0015--0.086 electrons per $1\ifmmode\times\else\texttimes\fi{}1$ unit cell), such that the silicon surface degenerates into a metal. The alters structure state causes rigid-band model to break down. parabolic-band approximation breaks down as well. These...
We have investigated the structure and properties of dithiothreitol (DTT) monolayers adsorbed on Au(111). Using scanning tunneling microscopy (STM), Auger electron spectroscopy (AES), we compared DTT with those more conventional octanethiol layers. STM measurements indicate that much layer is disordered; however, small ordered regions local 2√3×√3 symmetry are observed. images films exhibit characteristic close packed √3×√3 molecular c(4×2) supersymmetry. AES indicates sulfur coverage for...
Using scanning tunneling microscopy (STM), Auger electron spectroscopy, and low-energy diffraction, we have determined the optimal gold exposure for Ge(001) $c$(8 \ifmmode\times\else\texttimes\fi{} 2)-Au surface. We find deposition of submonolayer (ML) onto a surface held at temperatures between 570 870 K produces 2) reconstruction. The relative extent domains increases with Au exposure, 0.75 \ifmmode\pm\else\textpm\fi{} 0.05 ML is entirely covered by chains. 0.75-ML equivalent to six atoms...
We have made gap measurements at 4.2 K on the high-${T}_{c}$ superconductor ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.5+\mathrm{x}}$ by electron tunneling using a low-temperature scanning-tunneling microscope. In all samples studied we observe large variations in energy gap. very sharp with 2\ensuremath{\Delta}=5 meV yielding value of 2\ensuremath{\Delta}/${k}_{B}$${T}_{c}$=0.7, far below weak-coupling limit. The largest measure has 2\ensuremath{\Delta}=95 and indicates an...
Quantification of the effect partial dehalogenation on SAMN a bromo-substituted heterotriangulene molecule by comprehensive DFT/MC model.
The morphology of polyaniline electrochemically deposited onto a thermally evaporated gold electrode substrate has been investigated in the nucleation stages using scanning tunneling microscopy. films are grown galvanostatic mode at 70 μA/cm2 current density for 25, 50 and 100 s durations topography is measured air. results show that 25 s, coverage nuclei on sparse, but various shapes tend to connect partial coalescence. For deposition, population increases significantly resulting high...
We have performed both topographic and spectroscopic measurements at 4.2 K on thin films of YBa2Cu3Ox with a scanning tunneling microscope. The all had zero resistance temperatures in excess 75 K. found that, even low temperatures, most the surface were conducting. Images obtained voltages as 2 mV little effect resultant topography. Noisy patches, which are observed some images, result from unstable feedback response, indicate regions reduced conductivity. Current–voltage curves different...
We have studied the growth and structure of thin TiOx films on W(110) using Auger electron spectroscopy, low energy diffraction (LEED), scanning tunneling microscopy (STM). The procedure used to grow these includes deposition Ti metal onto surface followed by a saturation oxygen exposure. LEED STM reveal that several different ordered film structures can result depending upon initial amount deposited final annealing temperature. Specifically, oxidation anneal 1350 K one monolayer (ML)...
The epitaxy of Mg, a hexagonal-closed-packed (hcp) metal in the bulk, onto room-temperature body-centered-cubic Mo(001) substrate is investigated. A Stranski-Krastanov, layer by followed islands, growth mode observed including initial stabilization metastable face-centered-cubic (fcc) phase Mg. Layer persists for four layers. During first and second highly corrugated surface potential lattice mismatch both act to limit island size, proceeds via nucleation small two-dimensional islands....
We report on experiences operating over a dozen scanning tunneling microscopes in liquid helium at 4.2 K the past four years. The were both bimorph and tube scanner designs. Most of our (STMs) had ceramic frames, but as some early models survived only limited number thermal cycles (between room temperature temperatures) we also constructed with metal using titanium. calibration piezoelectric translators well adjustment for nonorthogonality scan directions are discussed. discuss various ways...
We study the self-assembly of halogen-based organic molecules on a passivated silicon surface. The room temperature adsorption 2,4,6-tris(4-iodophenyl)-1,3,5-triazine (TIPT) Si(111)-$\surd$3$\times$$\surd$3-Ag surface is described. investigated primarily by room-temperature scanning tunneling microscopy (STM) and density-functional theoretical (DFT) calculations. experimental results dramatic example how substrate can influence overall structure self-assembly. With increasing dose, TIPT...
We used a scanning tunnelling microscope (STM) to measure both the tunnel current, I, and dynamic conductance, dI/dV, at 4·2 K for number of high-transition temperature oxide superconductors. Large spatial variations in characteristics are observed. At low resistances, all samples show evidence single electron incremental charging. Results on BiSrCaCu2Ox coexistence charging with Josephson coupling between grains within sample. Bi sample crystal YBa2Cu3O6·5+x reveal possible energy gap (2A)...