315 research outputs found
The Synthescope: A Vision for Combining Synthesis with Atomic Fabrication
The scanning transmission electron microscope, a workhorse instrument in
materials characterization, is being transformed into an atomic-scale material
manipulation platform. With an eye on the trajectory of recent developments and
the obstacles toward progress in this field, we provide a vision for a path
toward an expanded set of capabilities and applications. We reconceptualize the
microscope as an instrument for fabrication and synthesis with the capability
to image and characterize atomic-scale structural formation as it occurs.
Further development and refinement of this approach may have substantial impact
on research in microelectronics, quantum information science, and catalysis
where precise control over atomic scale structure and chemistry of a few
"active sites" can have a dramatic impact on larger scale functionality and
where developing a better understanding of atomic scale processes can help
point the way to larger scale synthesis approaches
Approximate polynomial structure in additively large sets
We show that any subset of the natural numbers with positive logarithmic Banach
density contains a set that is within a factor of two of a geometric progression,
improving the bound on a previous result of the authors. Density conditions on
subsets of the natural numbers that imply the existence of approximate powers of
arithmetic progressions are developed and explore
Direct Imaging of Electron Orbitals with a Scanning Transmission Electron Microscope
Recent studies of secondary electron (SE) emission in scanning transmission
electron microscopes suggest that material's properties such as electrical
conductivity, connectivity, and work function can be probed with atomic scale
resolution using a technique known as secondary electron e-beam-induced current
(SEEBIC). Here, we apply the SEEBIC imaging technique to a stacked 2D
heterostructure device to reveal the spatially resolved electron orbital
ionization cross section of an encapsulated WSe2 layer. We find that the double
Se lattice site shows higher emission than the W site, which is at odds with
first-principles modelling of ionization of an isolated WSe2 cluster. These
results illustrate that atomic level SEEBIC contrast within a single material
is possible and that an enhanced understanding of atomic scale SE emission is
required to account for the observed contrast. In turn, this suggests that
subtle information about interlayer bonding and the effect on electron orbitals
can be directly revealed with this technique
Spectroscopic imaging of single atoms within a bulk solid
The ability to localize, identify and measure the electronic environment of
individual atoms will provide fundamental insights into many issues in
materials science, physics and nanotechnology. We demonstrate, using an
aberration-corrected scanning transmission microscope, the spectroscopic
imaging of single La atoms inside CaTiO3. Dynamical simulations confirm that
the spectroscopic information is spatially confined around the scattering atom.
Furthermore we show how the depth of the atom within the crystal may be
estimated.Comment: 4 pages and 3 figures. Accepted in Phys.Rev.Let
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