Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “aberration correction”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

E-beam manipulation of Si atoms on graphene edges with an aberration-corrected scanning transmission electron microscope

The burgeoning field of atomic-level material control holds great promise for future breakthroughs in quantum and memristive device manufacture and fundamental studies of atomic-scale chemistry. Realization of atom-by-atom control of matter represents a complex and ongoing challenge. Here, we explore the feasibility of controllable motion of dopant Si atoms at the edges of graphene via the sub-atomically focused electron beam in a scanning transmission electron microscope. Furthermore, we demonstrate that the graphene edges can be cleaned of Si atoms and then subsequently replenished from nearby source material. It is also shown how Si edge atoms may be “pushed” from the edge of a small hole into the bulk of the graphene lattice and from the bulk of the lattice back to the edge. This is accomplished through sputtering of the edge of the graphene lattice to bury or uncover Si dopant atoms. Finally, we demonstrate e-beam mediated hole healing and incorporation of dopant atoms. These experiments form an initial step toward general atomic-scale material control.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

A novel sector mass spectrograph design for high-order coded aperture Mass Spectrometry with stigmatic aberration correction

Previous works experimentally demonstrated that the application of spatially-coded apertures to simple sector mass spectrographs can result in increased signal intensity while maintaining spectral resolution comparable to that of a conventional slit aperture.[Chen, E.X., et al.: J Am Soc Mass Spectr. 26, 1633 (2015)][Russell, Z.E., et al.: J Am Soc Mass Spectr. 26, 248 (2015)] This spatial coding technique was later applied to a double-focusing Mattauch-Herzog mass spectrograph, and shown to be generally compatible with the architecture.[Russell, Z.E., et al.: J Am Soc Mass Spectr. 27, 1 (2016)] However, the achieved signal gain was limited by the spatial size of the electric sector gap. In this work, we introduce a modified version of the Mattauch-Herzog mass spectrograph with a wide-gap electric sector that is enabled by a novel, segmented-electrode approach, and show via simulation that this modified architecture alone (without aperture coding) achieves a 1.8x improvement in mass resolving power compared to a conventional Mattauch-Herzog spectrograph of equivalent size. Further, simulation of an aperture-coded version of the instrument supports a predicted signal strength increase of 50x with minimal loss of aperture clarity on the sensor due to the increased open area of the high-order coded aperture which can be passed.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Atomically resolved structure of ligand-protected Au{sub 9} clusters on TiO{sub 2} nanosheets using aberration-corrected STEM

Triphenylphosphine ligand-protected Au{sub 9} clusters deposited onto titania nanosheets show three different atomic configurations as observed by scanning transmission electron microscopy. The configurations observed are a 3-dimensional structure, corresponding to the previously proposed Au{sub 9} core of the clusters, and two pseudo-2-dimensional (pseudo-2D) structures, newly found by this work. With the help of density functional theory (DFT) calculations, the observed pseudo-2D structures are attributed to the low energy, de-ligated structures formed through interaction with the substrate. The combination of scanning transmission electron microscopy with DFT calculations thus allows identifying whether or not the deposited Au{sub 9} clusters have been de-ligated in the deposition process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Static characterization of a highly optimized streak tube design incorporating a steering slot anode and an aberration-corrected Einzel lens

The BHx streak tube, under development at the Laboratory for Laser Energetics, incorporates a series of novel electron-optics elements to enable high fidelity measurements for high-energy-density physics experiments. The system is engineered to support a 25-mm active photocathode region compatible with sub-picosecond temporal resolution and with 70% internal photoelectron throughput. It exhibits negligible geometric distortion on a flat output screen, making it well suited for variety of measurements, such as ultrafast x-ray spectroscopy. Here, this paper presents characterization data from a prototype unit tested with an ultraviolet laser in a static deflection (non-swept) mode and shows good agreement with the predictions from numerical modeling, including focusing performance and geometric distortion measurements. Key design elements have been demonstrated and de-risked, laying the foundation for dynamic deflection testing. The anticipated improvements in data fidelity are expected to impact the fields as diverse as inertial confinement fusion, laboratory astrophysics, and materials science.

High energy density physics↗
DOE OSTI2022

Visualization of defects in single-crystal and thin-film PdCoO 2 using aberration-corrected scanning transmission electron microscopy

Single-crystal delafossite PdCoO 2 is known to have an extremely low intrinsic impurity concentration of ~0.001%, demonstrating extraordinarily high conductivity with a mean free path of ~20 μm at low temperatures. However, when grown as thin films, the resistivity at room temperature increases by a factor of 3–80 times, depending on the film thickness. Using scanning transmission electron microscopy, we identify different classes of defects for the single crystal vs epitaxial thin film. The dominant defect for single-crystal PdCoO 2 is found to be ribbonlike defects. For the thin films, we identify different types of defects arising in epitaxial thin films mainly due to substrate termination that disrupt the lateral connectivity of the conducting planes. Further, our results are consistent with the high conductivity of single crystals and increased electrical resistivity of the thin films compared to that of single crystals, suggesting that selecting a proper substrate, improving surface quality, and reducing the step density are the keys to enhance the film quality for utilizing PdCoO 2 as a platform for future applications.

36 MATERIALS SCIENCE↗
DOE OSTI2019

PIE of Cycle 13 316SS Cladding Using Aberration Corrected STEM Image and Analys

Optical, SEM and TEM analysis confirmed the presence of moderate sensitization in the 20% cold worked 316SS after the iron aluminide coating was applied. The Cr depletion occurs on the grain boundaries between the closely spaced carbides, and at the interface between the carbides and matrix. Cr depletion varied from locally along the grain boundaries, in many cases showing levels down to 15 wt%, but a few isolated regions had depletion levels down to 12.5 wt%. Optical and SEM images taken from a weld heat affected zone revealed the recrystallization occurred after an end plug cap had been welded to the coated cladding. Irradiation did not affect the carbides in a noticeable manner, but radiation-induced segregation/depletion altered the Cr depletion profiles by removing the wide Cr depletion profile, and replacing it with a much deeper, more narrow profile. Cr levels were depleted to 8-10 wt%, Ni and Si were enriched to levels of 40 wt% and 12 wt% respectively. Substantial precipitation formed in the matrix, and on line dislocations in the matrix and on grain boundary dislocations. Voids were observed in the upper region of the TPBAR where the irradiation temperature exceeds 320C. The levels of Cr depletion and Ni/Si enrichment indicate a material in a state susceptible to irradiation assisted stress corrosion cracking.

316SS cladding↗