95 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
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
Polar-Graded Multiferroic SrMnO3 Thin Films
Engineering defects and strains in oxides provides a promising route for the quest of thin film materials with coexisting ferroic orders, multiferroics, with efficient magnetoelectric coupling at room temperature. Precise control of the strain gradient would enable custom tailoring of the multiferroic properties but presently remains challenging. Here we explore the existence of a polar-graded state in epitaxially strained antiferromagnetic SrMnO3 thin films, whose polar nature was predicted theoretically and recently demonstrated experimentally. By means of aberration-corrected scanning transmission electron microscopy we map the polar rotation of the ferroelectric polarization with atomic resolution, both far from and near the domain walls, and find flexoelectricity resulting from vertical strain gradients. The origin of this particular strain state is a gradual distribution of oxygen vacancies across the film thickness, according to electron energy loss spectroscopy. Herein we present a chemistry-mediated route to induce polar rotations in oxygen-deficient multiferroic films, resulting in flexoelectric polar rotations and with potentially enhanced piezoelectricity
- …