Helium Atom Scattering
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Using a state-of-the-art elastic and single phonon inelastic helium atom
scattering facility, we are exploring the effects of extended arrays of
defects on such phenomena as step dynamics, energy exchange, diffusion,
and adsorption. We have recently begun studying the structure and dynamics of
soft materials using helium atom scattering. We are also addressing
how surface forces, and hence bonding, differs at the surface and selvedge
region of a material as compared to bulk behavior. Metallic alloys are the
current focus of this endeavor. |
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Metallic Oxidation and Surface Metallurgy  |
We are exploring the atomic level processes and kinetic mechanisms
which are responsible for metallic oxidation. These efforts are focused on
the use of energetic oxidants such as high kinetic energy molecular oxygen
and atomic oxygen. Synergistic effects involving electron-stimulated and,
shortly, UV-enhanced surface oxidation are also being explored as part of
this effort. Surface metallurgical studies involving surface forces and
bonding of clean and molecular adsorbate-covered surfaces form an
important complement to the kinetic studies. |
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Polymer Dynamics
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Our atomic force microscope provides non-destructive imaging
technology to monitor polymer dynamics. Currently, we are tracking
individual defects in polymer thin films, observing phase separation
mechanisms due to various substrates, and monitoring microdomain movement
under stress or electric fields. |
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Polymer Defect Evolution
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Ultrathin diblock copolymer films have garnered much attention from
researchers in recent years as a system for studying the growth of
order. These materials exhibit a rich and complex set of kinetic
processes during formation that also hold promise for diverse
technological applications. Copolymer films will become more useful
as their mechanical properties are determined and their morphology
becomes more predictable and hence controllable. Particularly
elusive to researchers has been the discovery of the types of defects
that arise and evolve over time in these films. We have observed the
temporal evolution of individual defects in ultrathin diblock
copolymer films for the very first time. |
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Polymer Alignment
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Microphase separation creates islands and holes via film thickness
quantization in the direction perpendicular to the substrate while,
under carefully balanced thermodynamic conditions, microphase
separation can also expose both polymer components to the air/polymer
interface in the direction parallel to the substrate. This latter
phenomenon can generate spacially periodic microdomains consisting of
the different chemical constituents of the diblock, whose scale and
geometry reflect the chemical and physical properties of the polymer.
The repeat spacing of such microdomains can be precisely controlled
on the nanometer scale by changing, for example, the molecular weight
of the diblock copolymer. |
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Reactive Beam Scattering
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We are investigating the kinetics and dynamics of surface reactions
under controlled, ultra-high vacuum conditions. Combustion reactions and
various oxidation/reduction reactions on Rh(111) are currently being
explored. We are also studying the structure and
vibrational spectra of atoms and molecules adsorbed on various substrates,
using surface-sensitive He diffraction and inelastic He scattering.
Recent work has focused on the structure of ice overlayers. |
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Biological Microscopy
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Atomic force microscopy (AFM) was used as a novel approach to achieve enhanced
characterization of the three-dimensional fine structure and topology of cocci
from Staphylococcus aureus. To gain insight into the mechanism of resistance
to vancomycin in recently emerging glycopeptide-intermediate S. aureus (GISA),
strains were examined that were either susceptible or resistant to glycopeptides
and/or methicillin.
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Scanning Tunneling Microscopy
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In-situ STM measurements are being made of the step meandering and
doubling induced by trace oxidation of the Ni(977) surface. Oxidation of
Ni(111) is also being studied by STM as a function of oxygen exposure and
local electron injection. |
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Supersonic Molecular Beam Epitaxy  |
The use of reagent kinetic energy as a growth parameter during
molecular beam deposition of cubic silicon carbide on Si(001) is being
explored using supersonic beams of single source molecular precursors.
The lessons from this experiment are being applied in an attempt to
develop more efficient pathways for diamond growth. |
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Electrochemistry and Corrosion
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In-situ atomic force microscopy is being used to examine the
corrosion chemistry of metals, including pioneering studies of how
externally-applied stresses can modify the corrosion behavior of strategic
metals such as Ni, Al, and Al-2024T3 alloy. |
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