TEM and HREM Investigation of The Precipitation of Cobalt and Nickel In Polycrystalline Silicon

1991 ◽  
Vol 238 ◽  
Author(s):  
H. J. Möller ◽  
Juyong Chung ◽  
Lan Huang
Keyword(s):  
Grain Boundaries ◽  
Lattice Mismatch ◽  
Large Angle ◽  
Three Dimensional ◽  
Cobalt Disilicide ◽  
Surface Source ◽  
High Resolution Tem ◽  
Nickel Disilicide ◽  
Micrometer Size ◽  
Cobalt And Nickel

ABSTRACTThe precipitation behavior of cobalt and nickel at grain boundaries in multicrystalline silicon is investigated. The metals are diffused into the specimens from a surface source between 800 -1000 °C and the precipitation after cooling is studied by conventional and high resolution TEM. Cobalt and nickel disilicide precipitates nucleate both in the bulk and at grain boundaries. They form few large (micrometer size) plate-like or three-dimensional precipitates depending on the cooling rate. Cobalt disilicide with a slightly larger lattice mismatch has a higher tendency to nucleate at large angle grain boundaries. Both suicides nucleate preferentially at coherent twin boundaries forming a few atomic layers thick platelet parallel to the {111} twin plane. HREM and image simulations are performed to analyze the Si / MS12 / twin interface structure (M = Co, Ni).

The Precipitation of Nickel and Copper at Grain Boundaries in Silicon

1990 ◽  
Vol 209 ◽  
Author(s):  
H. J. Möller ◽  
U. Jendrich ◽  
L. Huang ◽  
A. Foitzik
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Point Defects ◽  
Polycrystalline Silicon ◽  
Three Dimensional ◽  
Surface Source ◽  
Native Point Defects ◽  
Micrometer Size

ABSTRACTThe precipitation of copper and nickel at grain boundaries in cast polycrystalline silicon is investigated. The metals are diffused into the specimens from a surface source between 800 – 1000 °C and the precipitation after cooling is studied by TEM. Copper precipitates in form of colonies containing hundreds of particles with a size between 5–6 nm. In the grain boundary they nucleate preferentially at dislocations and steps. The distribution and size of the precipitates depend on the cooling rate after the diffusion. Nickel forms only few large (micrometer size) plate-like or three dimensional precipitates at and near grain boundaries. The main features of the results and the differences between the two elements are explained under the assumption that the precipitation requires the transport of native point defects.

Structural analysis of a Σ5 grain boundary in YBa2Cu3O7δ

1993 ◽  
Vol 51 ◽  
pp. 942-943
Author(s):  
J.-Y. Wang ◽  
Y. Zhu ◽  
A.H. King ◽  
M. Suenaga
Keyword(s):  
Grain Boundary ◽  
Lattice Mismatch ◽  
Weak Link ◽  
Coincidence Site Lattice ◽  
Large Angle ◽  
Dislocation Core ◽  
Superconducting Order Parameter ◽  
Outstanding Problem ◽  
Transmission Electron

One outstanding problem in YBa2Cu3O7−δ superconductors is the weak link behavior of grain boundaries, especially boundaries with a large-angle misorientation. Increasing evidence shows that lattice mismatch at the boundaries contributes to variations in oxygen and cation concentrations at the boundaries, while the strain field surrounding a dislocation core at the boundary suppresses the superconducting order parameter. Thus, understanding the structure of the grain boundary and the grain boundary dislocations (which describe the topology of the boundary) is essential in elucidating the superconducting characteristics of boundaries. Here, we discuss our study of the structure of a Σ5 grain boundary by transmission electron microscopy. The characterization of the structure of the boundary was based on the coincidence site lattice (CSL) model.Fig.l shows two-beam images of the grain boundary near the projection. An array of grain boundary dislocations, with spacings of about 30nm, is clearly visible in Fig. 1(a), but invisible in Fig. 1(b).

Effect Of Phosphorus On Ge/Si(001) Island Formation

2002 ◽  
Vol 737 ◽  
Author(s):  
Theodore I. Kamins ◽  
Gilberto Medeiros-Ribeiro ◽  
Douglas A. A. Ohlberg ◽  
R. Stanley Williams
Keyword(s):  
Deposition Rate ◽  
Strain Energy ◽  
Competitive Adsorption ◽  
Lattice Mismatch ◽  
Three Dimensional ◽  
Deposition Process ◽  
Thin Layers ◽  
Island Size ◽  
Partial Pressures ◽  
Intermediate Size

ABSTRACTWhen Ge is deposited epitaxially on Si, the strain energy from the lattice mismatch causes the Ge in layers thicker than about four monolayers to form distinctive, three-dimensional islands. The shape of the islands is determined by the energies of the surface facets, facet edges, and interfaces. When phosphorus is added during the deposition, the surface energies change, modifying the island shapes and sizes, as well as the deposition process. When phosphine is introduced to the germane/hydrogen ambient during Ge deposition, the deposition rate decreases because of competitive adsorption. The steady-state deposition rate is not reached for thin layers. The deposited, doped layers contain three different island shapes, as do undoped layers; however, the island size for each shape is smaller for the doped layers than for the corresponding undoped layers. The intermediate-size islands are the most significant; the intermediate-size doped islands are of the same family as the undoped, multifaceted “dome” structures, but are considerably smaller. The largest doped islands appear to be related to the defective “superdomes” discussed for undoped islands. The distribution between the different island shapes depends on the phosphine partial pressure. At higher partial pressures, the smaller structures are absent. Phosphorus appears to act as a mild surfactant, suppressing small islands.

Atomic structure of [0001]-tilt grain boundaries in ZnO:  A high-resolution TEM study of fiber-textured thin films

2004 ◽  
Vol 70 (12) ◽  
Author(s):  
Fumiyasu Oba ◽  
Hiromichi Ohta ◽  
Yukio Sato ◽  
Hideo Hosono ◽  
Takahisa Yamamoto ◽  
...  
Keyword(s):  
Thin Films ◽  
High Resolution ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
High Resolution Tem

Van der Waals Epitaxy of GaSe on GaAs(111)

1994 ◽  
Vol 340 ◽  
Author(s):  
L. E. Rumaner ◽  
F.S. Ohuchi
Keyword(s):  
Lattice Mismatch ◽  
Van Der Waals ◽  
Three Dimensional ◽  
Structured Materials ◽  
Lattice Matching ◽  
Molecular Beam Deposition ◽  
Crystal Films ◽  
Low Dimensional ◽  
Matching Constraints ◽  
Lattice Matched

ABSTRACTAlthough heteroepitaxy of lattice-matched and lattice-mismatched materials leading to artificially structured materials has resulted in impressive performance in various electronics devices, material combinations are usually limited by lattice matching constraints. A new concept for fabricating material systems using the atomically abrupt and low dimensional nature of layered materials, called van der Waals epitaxy (VDWE), has been developed. GaSe (Eg = 2.1 eV) has been deposited on the three dimensional surface of GaAs (111) using a molecular beam deposition system. GaSe was evaporated from a single Knudsen source, impinging on a heated substrate. Even with a lattice mismatch of 6% between the substrate and the growing film, good quality single crystal films were grown as determined by RHEED. The films have further been analyzed using a complementary combination of XPS and X-ray reflectivity.

Three-Dimensional Hexagonal Close-Packed Superlattices of Passivated Ag Nanocrystals

1997 ◽  
Vol 3 (S2) ◽  
pp. 431-432
Author(s):  
S. A. Harfenist ◽  
Z. L. Wang ◽  
R. L. Whetten ◽  
I. Vezmar ◽  
M. M. Alvarez ◽  
...  
Keyword(s):  
Carbon Film ◽  
Three Dimensional ◽  
Structure Characterization ◽  
Self Assembled Monolayers ◽  
Hexagonal Close Packed ◽  
Self Assembling ◽  
Transmission Electron ◽  
Assembled Monolayers ◽  
High Resolution Tem ◽  
Nanocrystal Superlattices

Silver nanocrystals passivated by dodecanethiol self-assembled monolayers were produced using an aerosol technique described in detail elsewhere [1]. Self-assembling passivated nanocrystal-superlattices (NCS's) involve self-organization into monolayers, thin films, and superlattices of size-selected nanoclusters encapsulated in a protective compact coating [2,3,4,5,6,7]. We report the preparation and structure characterization of three-dimensional (3-D) hexagonal close-packed Ag nanocrystal supercrystals from Ag nanocrystals of ˜4.5 nm in diameters. The crystallography of the superlattice and atomic core lattices were determined using transmission electron microscopy (TEM) and high-resolution TEM.SEM was used to image the nanocrystal superlattices formed on an amorphous carbon film of an TEM specimen grid (fig. la). The superlattice films show well shaped, sharply faceted, triangular shaped sheets. Figure lb depicts numerous Ag nanocrystal aggregates uniformly distributed over the imaging region. Inset in this figure is an enlargement of the boxed region at the edge of a supercrystal typifying the ordered nanocrystal packing.

Some Remarks on the Behaviour of Surface Source Distributions near the Edge of a Body

1973 ◽  
Vol 24 (1) ◽  
pp. 25-33
Author(s):  
J W Craggs ◽  
K W Mangler ◽  
M Zamir
Keyword(s):  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Symmetric Case ◽  
The Body ◽  
Dimensional Problem ◽  
Surface Source ◽  
Asymmetric Case ◽  
Main Flow Direction ◽  
Flow Plane

SummaryWhen the incompressible potential flow past a three-dimensional body is represented by source distributions on the body surface, these source distributions have singularities near an edge or corner, for example á trailing edge of a wing or the (unfaired) intersection of a body and a wing. The nature of these singularities is discussed. When assuming slow variations of the geometry in the main flow direction we can consider a two-dimensional problem in the cross-flow plane. Here the tangential velocities and source distributions are proportional to certain powers of the distance from the corner. For example at a convex right-angled corner these powers are − ⅓ in the asymmetric case (the bisector is a potential line) and ⅓ in the symmetric case (the bisector is a streamline) for both sources and tangential velocities. At a concave right-angled corner the corresponding values for the source distributions are ⅓ (asymmetric case) and − ⅓ (symmetric case) whereas they are 1 and 3 respectively for the tangential velocities.

The Effect of Severe Plastic Deformation on the Brittle-Ductile Transition in Low Carbon Steel

2009 ◽  
Vol 633-634 ◽  
pp. 471-480
Author(s):  
Masaki Tanaka ◽  
Kenji Higashida ◽  
Tomotsugu Shimokawa
Keyword(s):  
Fracture Toughness ◽  
Carbon Steel ◽  
Grain Boundaries ◽  
Three Dimensional ◽  
Low Carbon Steel ◽  
Dislocation Dynamics ◽  
Strain Rates ◽  
Low Carbon ◽  
Dislocation Source ◽  
Brittle Ductile Transition

Brittle-ductile transition (BDT) behaviour was investigated in low carbon steel deformed by an accumulative roll-bonding (ARB) process. The temperature dependence of its fracture toughness was measured by conducting four-point bending tests at various temperatures and strain rates. The fracture toughness increased while the BDT temperature decreased in the specimens deformed by the ARB process. Arrhenius plots between the BDT temperatures and the strain rates indicated that the activation energy for the controlling process of the BDT was not changed by the deformation with the ARB process. It was deduced that the decrease in the BDT temperature by grain refining was not due to the increase in the dislocation mobility controlled by short-range barriers. Quasi-three-dimensional simulations of dislocation dynamics, taking into account of crack tip shielding due to dislocations, were performed to investigate the effect of a dislocation source spacing along a crack front on the BDT. The simulation indicated that the BDT temperature is decreased with decreasing in the dislocation source spacing. Molecular dynamics simulations revealed that moving dislocations were impinged against grain boundaries and were reemitted from there with increasing strain. It indicates that grain boundaries can be new sources in ultra-fine grained materials, which increases toughness at low temperatures.

Transmission Electron Diffraction Techniques for Nm Scale Strain Measurement in Semiconductors

1995 ◽  
Vol 405 ◽  
Author(s):  
J. Vanhellemont ◽  
K. G. F. Janssens ◽  
S. Frabboni ◽  
P. Smeys ◽  
R. Balboni ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Large Angle ◽  
Three Dimensional ◽  
Local Strain ◽  
Quantitative Information ◽  
Contrast Imaging ◽  
Transmission Electron ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Convergent Beam

AbstractAn overview is given of transmission electron microscopy techniques to address strain with nm scale spatial resolution. In particular the possibilities and limitations of (large angle) convergent beam electron diffraction ((LA)CBED) and electron diffraction contrast imaging (EDCI) techniques are discussed in detail. It will be shown by a few case studies that unique and quantitative information on local strain distributions can be obtained by the combined use of both (LA)CBED and EDCI in correlation with three dimensional finite element simulations of the strain distributions in the thinned specimen.

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