scholarly journals Untangling competition between epitaxial strain and growth stress through examination of variations in local oxidation

2021 ◽  
Author(s):  
Maria Yankova ◽  
Alistair Garner ◽  
Felicity Baxter ◽  
Samual Armson ◽  
Christopher Race ◽  
...  
Keyword(s):  
High Performance ◽  
High Resolution Electron Microscopy ◽  
Growth Stress ◽  
Length Scales ◽  
Epitaxial Strain ◽  
Multiple Length Scales ◽  
Resolution Electron ◽  
Local Oxidation ◽  
Corrosion Mechanisms ◽  
Microscopy Techniques

Abstract Understanding oxide formation during corrosion of high-performance alloys in harsh environments is of great fundamental and industrial interest and provides a potential route for reducing the significant annual cost of corrosion globally. However, corrosion mechanisms involve multiple length scales, requiring a multitude of advanced experimental procedures. Here, we use correlated high resolution electron microscopy techniques over a range of length scales, combined with crystallographic modelling to show that there is a clear competition between epitaxial strain and growth stress during oxidation. The degree to which these competing mechanisms operate is shown to depend on the orientation of the substrate grains leading to significant local variations in oxide microstructure and thus protectiveness, even across a single sample. This leads to the possibility of tailoring substrate crystallographic textures in order to promote gradual phase transformation and the development of stress driven, well-oriented protective oxides, and so to improving overall corrosion performance.

Micro-engineered Nanowire Electron Source for Atomic Resolution Imaging

2021 ◽  
Author(s):  
Han Zhang ◽  
Yu Jimbo ◽  
Akira Niwata ◽  
Akihiro Ikeda ◽  
Akira Yasuhara ◽  
...  
Keyword(s):  
Electron Beam ◽  
High Performance ◽  
Low Cost ◽  
High Resolution Electron Microscopy ◽  
Electron Source ◽  
Atomic Resolution ◽  
Angular Deviation ◽  
Resolution Electron ◽  
Emission Volume ◽  
Forming Efficiency

Abstract The size tunability and chemical versatility of nanostructures provide attractive engineering potential to realize an electron source of high brightness and spatial temporal coherence, which is a characteristic ever pursued by high resolution electron microscopy. (1–3) Regardless of the intensive research efforts, electron sources that have ever produced atomic resolution images are still limited to the conventional field emitters based on a bulk W needle. It is due to the lack of fabrication precision for nanostructured sources, that is required to align a nanometric emission volume along a macroscopic emitter axis with sub-degree angular deviation. (4) In this work, we produced a LaB6 nanowire electron source which was micro-engineered to ensure a highly collimated electron beam with perfect lateral and angular alignment. Such electron source was validated by installing in an aberration-corrected transmission electron microscope, where atomic resolution in both broad-beam and probe-forming modes were demonstrated at 60kV beam energy. The recorded un-monochromated 0.20eV electron energy loss spectroscopy (EELS) resolution, together with 20% probe forming efficiency and 0.4% probe current peak-to-peak noise ratio under a wide vacuum range, presented the unique advantages of nanotechnology and promised high performance low-cost electron beam instruments.

Characterization of Inconel/Carbon Multilayer Structures

1991 ◽  
Vol 238 ◽  
Author(s):  
J. Liu ◽  
Y. Cheng ◽  
M. W. Lund ◽  
Q. Wang ◽  
A. Higgs
Keyword(s):  
High Resolution Electron Microscopy ◽  
Optical Systems ◽  
Multilayer Structures ◽  
High Angle ◽  
Dc Magnetron Sputtering ◽  
X Ray ◽  
X Ray Scattering ◽  
Resolution Electron ◽  
Microscopy Techniques

ABSTRACTDC magnetron sputtering technique is used to fabricate inconel/carbon multilayers (ML) for applications in soft x-ray optical systems. The ML films were characterized by small angle x-ray scattering (SAXS), high resolution electron microscopy (HREM) and high-angle annular darkfield (HAADF) microscopy techniques. The HREM showed that the ML films are composed of smooth layers of amorphous components. The HAADF showed strong interdiffusion between inconel and carbon. There is no indication of any pure inconel or carbon regions in the ML films.

Microstructure of ELO-GaN Layers Grown by Hydride Vapor Phase Epitaxy

2001 ◽  
Vol 693 ◽  
Author(s):  
Silvija Gradecak ◽  
Volker Wagner ◽  
Marc Ilegems ◽  
Fabienne Bobard ◽  
Pierre Stadelmann
Keyword(s):  
Electron Microscopy ◽  
Vapor Phase ◽  
Vertical Direction ◽  
High Resolution Electron Microscopy ◽  
Growth Conditions ◽  
Vapor Phase Epitaxy ◽  
Hydride Vapor Phase Epitaxy ◽  
Initial Stage ◽  
Resolution Electron ◽  
Microscopy Techniques

AbstractElectron microscopy techniques are applied to investigate structural properties of GaN layers selectively grown by hydride vapor phase epitaxy on crystalline and amorphous GaN seed layers deposited on (0001)Al2O3 substrates. Optimalization of the growth conditions lead to a reduction both of the stacking fault concentration and c-axis tilting in the laterally grown regions. During the lateral growth threading dislocations from the seed layer bend from vertical direction of propagation. Bending behavior depends on the type of the dislocation and on the shape of the GaN film in the initial stage of the growth. Optical properties of laterally grown regions are correlated with the high point-defect incorporation that is revealed by high-resolution electron microscopy.

Static and Dynamic Characteristics of Thermoelectric Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 826-830
Author(s):  
Tsuyoshi Kajitani ◽  
Yuzuru Miyazaki ◽  
Yasuhuri Ono ◽  
Shahnaz Begum ◽  
Kunio Yubuta
Keyword(s):  
High Performance ◽  
Structural Characteristics ◽  
High Resolution Electron Microscopy ◽  
Low Energy ◽  
Double Layers ◽  
Energy Excitation ◽  
Resolution Electron ◽  
Different Types ◽  
2D Crystals ◽  
Weak Chemical

Structural characteristics of the high performance cobaltite thermoelectric semiconductors have been studied intensively by means of X-ray and neutron diffraction measurements and high resolution electron microscopy (HREM). These cobaltites consists of CoO2 triangular conducting sheets and several different types of block layers, i.e., Na, Ca, Sr single layers, three or four layered rock-salt layers, where Co-O2 square lattices are situated at their middle, and Bi-O or Tl-O double layers plus alkaline oxygen layers. Cold neutron scattering technique is employed to search possible low-energy excitation modes, being unique for nearly 1D and 2D crystals, and phonon density of states, DOS, of several high performance cobaltites at temperatures in the range from 10K to the ambient. Low energy, i.e., less than 2meV, excitation modes were found in the three different thermoelectric ceramics, i.e., γ -Na0.7CoO2, [Ca2CoO3]pCoO2, and [Ca2(Cu,Co)2O4]pCoO2. Possible origin of these low energy excitations are discussed in terms of low-energy corrugation mode generated due to weak chemical bondings, for which Van-der-Waals force dominates, between the CoO2 conduction sheets. These characteristics could be the key to realize low thermal conductivity and high-ZT of these ceramics.

scholarly journals TEM Studies of Precipitate Growth at the Atomic Level

1985 ◽  
Vol 62 ◽  
Author(s):  
J. M. Howe ◽  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Atomic Level ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Precipitate Growth ◽  
Convergent Beam ◽  
Microscopy Techniques

ABSTRACTRecent advances in transmission electron microscopy instrumentation and technique now make it possible to study the shape-evolution of precipitates in metallic alloys at the atomic level. This investigation demostrates how a combination of transmission electron microscopy techniques; namely, high-resolution electron microscopy, image simulation, energy-dispersive x-ray spectroscopy and convergent-beam electron diffraction are used to characterize the atomic structures, chemistry and growth mechanisms of γ' precipitate plates in an Al-4.2 a/o Ag alloy aged for 30 min. at 350°C. The complimentary information obtained from each of these techniques allows modelling of the growth process at the atomic level, thus providing insight into the basic precipitation behavior of alloys.

scholarly journals Yeast pex1 cells contain peroxisomal ghosts that import matrix proteins upon reintroduction of Pex1

2015 ◽  
Vol 211 (5) ◽  
pp. 955-962 ◽  
Author(s):  
Kèvin Knoops ◽  
Rinse de Boer ◽  
Anita Kram ◽  
Ida J. van der Klei
Keyword(s):  
Cross Sections ◽  
Matrix Protein ◽  
Protein Import ◽  
Electron Tomography ◽  
High Resolution Electron Microscopy ◽  
Matrix Proteins ◽  
Peroxisomal Membrane ◽  
Resolution Electron ◽  
Microscopy Techniques ◽  
Aaa Atpases

Pex1 and Pex6 are two AAA-ATPases that play a crucial role in peroxisome biogenesis. We have characterized the ultrastructure of the Saccharomyces cerevisiae peroxisome-deficient mutants pex1 and pex6 by various high-resolution electron microscopy techniques. We observed that the cells contained peroxisomal membrane remnants, which in ultrathin cross sections generally appeared as double membrane rings. Electron tomography revealed that these structures consisted of one continuous membrane, representing an empty, flattened vesicle, which folds into a cup shape. Immunocytochemistry revealed that these structures lack peroxisomal matrix proteins but are the sole sites of the major peroxisomal membrane proteins Pex2, Pex10, Pex11, Pex13, and Pex14. Upon reintroduction of Pex1 in Pex1-deficient cells, these peroxisomal membrane remnants (ghosts) rapidly incorporated peroxisomal matrix proteins and developed into peroxisomes. Our data support earlier views that Pex1 and Pex6 play a role in peroxisomal matrix protein import.

Structural Characterization Of Laser Lift-Off GaN

2000 ◽  
Vol 617 ◽  
Author(s):  
Eric A. Stach ◽  
M. Kelsch ◽  
W.S. Wong ◽  
E.C. Nelson ◽  
T. Sands ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Chemical Characterization ◽  
High Resolution Electron Microscopy ◽  
Economic Benefits ◽  
Thin Layers ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Lift Off ◽  
Microscopy Techniques

AbstractLaser lift-off and bonding has been demonstrated as a viable route for the integration of III-nitride opto-electronics with mainstream device technology. A critical remaining question is the structural and chemical quality of the layers following lift-off. In this paper, we present detailed structural and chemical characterization of both the epitaxial layer and the substrate using standard transmission electron microscopy techniques. Conventional diffraction contrast and high resolution electron microscopy indicate that the structural alteration of the material is limited to approximately the first 50 nm. Energy dispersive electron spectroscopy line profiles show that intermixing is also confined to similar thicknesses. These results indicate that laser lift-off of even thin layers is likely to result in materials suitable for device integration. Additionally, because the damage to the sapphire substrate is minimal, it should be possible to polish and re-use these substrates for subsequent heteroepitaxial growths, resulting in significant economic benefits.

Local Microstructural Organization in Carbogenic Molecular Sieves

1996 ◽  
Vol 431 ◽  
Author(s):  
Michael S. Kane ◽  
Henry C. Foley
Keyword(s):  
Neutron Diffraction ◽  
Molecular Sieves ◽  
Driving Forces ◽  
High Resolution Electron Microscopy ◽  
Complex Materials ◽  
Ordered Structures ◽  
Length Scales ◽  
Resolution Electron ◽  
High Degree ◽  
Molecular Sieving

AbstractThe microstructure of nanoporous, carbogenic molecular sieves (CMS) was studied using high resolution electron microscopy and neutron diffraction. The narrow range of pore sizes observed in these complex materials suggests that although these materials are globally amorphous, the local microstructural features are more organized. Our work, focused on poly(furfuryl alcohol)-derived CMS, is aimed at characterizing the evolution of this microstructure. Microscopy results show that materials synthesized at low temperature have some degree of organization but that the microstructure is featureless and symmetric at longer length scales. This symmetry is broken at higher synthesis temperatures as thermodynamic driving forces lead to further organization of the carbon atoms into more ordered structures but the length scales remain short. Micrographs of high temperature CMS show a high degree of curvature and features reminiscent of fullerene. The connectivity of the carbon atoms in the CMS has been probed using powder neutron diffraction. This data suggests that the atoms in the CMS form ordered structures on the length scale of 15Å which are distinctly different from the structure of graphite. These observed changes in the microstructure directly impact the adsorptive and molecular sieving characteristics of the CMS as illustrated by the marked differences between the diffusivities of oxygen and nitrogen. This property is crucial for the very demanding separation of nitrogen from oxygen in air.

3D electron microscopy investigations of human dentin at the micro/nano-scale using focused ion beam based nanostructuring

RSC Advances ◽  
2015 ◽  
Vol 5 (10) ◽  
pp. 7196-7199 ◽  
Author(s):  
Meltem Sezen ◽  
Sina Sadighikia
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
High Resolution Electron Microscopy ◽  
High Definition ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Human Dentin ◽  
Microscopy Techniques

In this study, high resolution electron microscopy techniques, such as Focused Ion Beam (FIB), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) allowed for revealing micro/nano features within human dentin with high definition and accuracy.

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