Quantitative High Resolution Electron Microscopy of Grain Boundaries and Comparison with Atomistic Simulations

2001 ◽  
Vol 7 (S2) ◽  
pp. 244-245
Author(s):  
G.H. Campbell ◽  
W.E. King ◽  
J.M. Plitzko ◽  
J. Belak ◽  
S.M. Foiles
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Radiation Effects ◽  
Crystal Defects ◽  
Boundary Structure ◽  
Atomistic Simulations ◽  
Simulated Image ◽  
Good Test

The technique of high-resolution transmission electron microscopy (HREM) produces images that contain information about the atomic structure of the specimen. Within additional, very stringent, constraints, the HREM image can contain information about atomic structure of crystal defects, including grain boundaries and interfaces. to extract this information from the image it is necessary to compare the experimental image with a simulated image calculated based upon an atomic model of the specimen.2 in this comparison, investigators have been aided by the use of quantitative techniques.Atomistic simulations are often used to predict the atomic structure of crystal defects or to simulate the evolution of dynamic processes in crystals, e.g. radiation effects or dislocation motion and interaction. During the development of new models of interatomic interactions, the predictions of simulations are tested against experimental observations to validate new potentials. Grain boundary structure is a good test because atoms residing in the boundary experience environments (interatomic distances and angles) that are significantly different from those experienced by atoms residing in a perfect crystal lattice site.

High-resolution EM study of submicrometer-grained Al-Mg solid solution alloys

1995 ◽  
Vol 53 ◽  
pp. 524-525
Author(s):  
Z. Horita ◽  
D. J. Smith ◽  
M. Furukawa ◽  
M. Nemoto ◽  
R. Z. Valiev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Grain Boundaries ◽  
Energy State ◽  
High Energy ◽  
Grain Structure ◽  
Boundary Structure ◽  
Solid Solution Alloy ◽  
Average Grain Size

It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

HREM Analysis of ∑3 ﹛112﹜ Tilt Grain Boundaries in Au Bicrystals Observed in Projection

2000 ◽  
Vol 6 (S2) ◽  
pp. 1044-1045
Author(s):  
C.J.D. Hetherington ◽  
U. Dahmen
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Thin Layer ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Phase 1 ◽  
High Resolution Electron Microscopy ◽  
Twin Plane ◽  
Stacking Fault ◽  
Resolution Electron

Grain boundaries in fee metals with low stacking fault energy are known to undergo extended relaxations that can at times lead to a thin layer of a different structure. In Cu, for example, it has been found that ∑3﹛ 112﹜ boundaries relax into a 9R phase [1]. In this work, we have used high resolution electron microscopy to investigate the atomic structure of ∑3 grain boundaries in mazed bicrystal films of Au. Using ﹛111﹜ Ge surfaces as a template, Au bicrystals can be grown in two orientation variants, related to each other by a 60° rotation about the surface normal. As described previously, such films have a strong tendency to facet onto the coherent twin plane parallel to the substrate [2], also known as “double positioning” [3]. If films are made very thin, the likelihood for such in-plane boundaries to lie in the foil decreases, and it becomes possible to observe the atomic structure of edge-on interfaces along <111>.

Atomic Structure Of Grain Boundaries And Interfaces In Iiinitrides Epitaxial Systems

1997 ◽  
Vol 482 ◽  
Author(s):  
S. Ruvimov ◽  
Z. Liliental-Weber ◽  
J. Washburn ◽  
H. Amano ◽  
I. Akasaki ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Stacking Faults ◽  
High Resolution Electron Microscopy ◽  
Epitaxial Layers ◽  
Resolution Electron

AbstractHigh resolution electron microscopy (HREM) was applied to study atomic structure of stacking faults, grain boundaries and interfaces in III-nitrides epitaxial layers grown by MOVPE on sapphire. Defects formed in GaN epitaxial layers grown by MOVPE were reviewed in comparison with those in MBE grown materials

Structure of Low- And High-Angle Grain Boundaries In YBCO/MgO Films

1998 ◽  
Vol 4 (S2) ◽  
pp. 676-677
Author(s):  
S. Oktyabrsky ◽  
R. Kalyanaraman ◽  
K. Jagannadham ◽  
J. Narayan
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Boundary Plane ◽  
Dislocation Model ◽  
High Angle ◽  
Transmission Electron

Grain boundaries (GBs) in laser deposited YB2Cu3O7-δ/MgO(001) thin films have been investigated by high-resolution transmission electron microscopy (TEM) and scanning TEM (STEM). We report both statistics and atomic structure of low-angle and high-angle [001] tilt grain boundaries resulting from almost perfect c-axis textured YBCO films.Atomic structure of low-angle GBs was analyzed using a dislocation model. These boundaries have been found to be aligned primarily along (100) and (110) interface planes. For (100) boundary plane, the GB consists of a periodic array of [100] dislocations (Fig.l). For (110) boundary plane, the array is also periodic but every [110] dislocation is split by ∼ 1.5 nm into two [100] and [010] dislocations (Fig.2). We have calculated energy of various configurations and shown that the energy of the (110) boundary with dissociated dislocations is comparable to that of (100) boundary, which explains the coexistence of (100) and (110) interface facets along the boundary.

Observations of grain boundary structure in submicrometer-grained Cu and Ni using high-resolution electron microscopy

1998 ◽  
Vol 13 (2) ◽  
pp. 446-450 ◽  
Author(s):  
Zenji Horita ◽  
David J. Smith ◽  
Minoru Nemoto ◽  
Ruslan Z. Valiev ◽  
Terence G. Langdon
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Nonequilibrium State ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Typical Feature ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Resolution Electron

Submicrometer-grained (SMG) structures were produced in Cu and Ni using an intense plastic straining technique, and the grain boundaries and their vicinities were observed by high-resolution electron microscopy. The grain boundaries exhibited zigzag configurations with irregular arrangements of facets and steps, and thus they were found to be in a high-energy nonequilibrium state. A similar conclusion was reached earlier for SMG Al–Mg solid solution alloys which have much lower melting points than Cu and Ni, suggesting that nonequilibrium grain boundaries are a typical feature of metals processed by intense plastic straining.

Surface reconstructions of (001) cleaved GdBa2Cu3O7-δ

1992 ◽  
Vol 50 (1) ◽  
pp. 106-107
Author(s):  
H.W. Zandbergen ◽  
M.R. McCartney
Keyword(s):  
Electron Microscopy ◽  
Copper Oxide ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Oxygen Deficiency ◽  
Surface Layers ◽  
Layer Sequence ◽  
Surface Reconstructions ◽  
Good Agreement

Very few electron microscopy papers have been published on the atomic structure of the copper oxide based superconductor surfaces. Zandbergen et al. have reported that the surface of YBa2Cu3O7-δ was such that the terminating layer sequence is bulk-Y-CuO2-BaO-CuO-BaO, whereas the interruption at the grain boundaries is bulk-Y-CuO2-BaO-CuO. Bursill et al. reported that HREM images of the termination at the surface are in good agreement with calculated images with the same layer sequence as observed by Zandbergen et al. but with some oxygen deficiency in the two surface layers. In both studies only one or a few surfaces were studied.

Atomic structure imaging of the Si/SiO2 interface with high-resolution electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 390-391
Author(s):  
J.L. Batstone ◽  
J.M. Gibson ◽  
Alice.E. White ◽  
K.T. Short
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Atomic Structure ◽  
High Resolution Electron Microscopy ◽  
Medium Voltage ◽  
Voltage Electron ◽  
Resolution Electron ◽  
Structural Image ◽  
Electron Microscopes ◽  
Point To Point

High resolution electron microscopy (HREM) is a powerful tool for the determination of interface atomic structure. With the previous generation of HREM's of point-to-point resolution (rpp) >2.5Å, imaging of semiconductors in only <110> directions was possible. Useful imaging of other important zone axes became available with the advent of high voltage, high resolution microscopes with rpp <1.8Å, leading to a study of the NiSi2 interface. More recently, it was shown that images in <100>, <111> and <112> directions are easily obtainable from Si in the new medium voltage electron microscopes. We report here the examination of the important Si/Si02 interface with the use of a JEOL 4000EX HREM with rpp <1.8Å, in a <100> orientation. This represents a true structural image of this interface.

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