A new dissociation mode for dislocations in silicon

1978 ◽  
Vol 36 (1) ◽  
pp. 346-347
Author(s):  
A. Ourmazd ◽  
G.R. Booker ◽  
C.J. Humphreys
Keyword(s):  
Detailed Examination ◽  
Experimental Results ◽  
Dislocation Network ◽  
Weak Beam ◽  
Phosphorus Doped

A (111) phosphorus-doped Si specimen, thinned to give a TEM foil of thickness ∼ 150nm, contained a dislocation network lying on the (111) plane. The dislocation lines were along the three <211> directions and their total Burgers vectors,ḇt, were of the type , each dislocation being of edge character. TEM examination under proper weak-beam conditions seemed initially to show the standard contrast behaviour for such dislocations, indicating some dislocation segments were undissociated (contrast A), while other segments were dissociated to give two Shockley partials separated by approximately 6nm (contrast B) . A more detailed examination, however, revealed that some segments exhibited a third and anomalous contrast behaviour (contrast C), interpreted here as being due to a new dissociation not previously reported. Experimental results obtained for a dislocation along [211] with for the six <220> type reflections using (g,5g) weak-beam conditions are summarised in the table below, together with the relevant values.

Flame retardance of modified graphene to pure cotton fabric

2017 ◽  
Vol 36 (2) ◽  
pp. 111-128 ◽  
Author(s):  
Hong Liu ◽  
Yang Du ◽  
Guohai Yang ◽  
Guoqing Zhu ◽  
Yunji Gao ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Flame Retardant ◽  
Cotton Fabric ◽  
Combustion Process ◽  
Experimental Results ◽  
Graphene Oxides ◽  
Nitrogen Doped ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene ◽  
Phosphorus Doped

Phosphorus- and nitrogen-doped graphene oxides are conveniently obtained by the modification of as-prepared graphene oxide and characterized by scanning electron microscopy, X-ray powder diffraction, Fourier-transform infrared, and ultraviolet–visible spectra. The combustion performances of pure cotton fabric, respectively, enriched with graphene oxide, phosphorus-doped graphene oxide, and nitrogen-doped graphene oxides, are tested and evaluated. The results show that phosphorus-doped graphene oxide acts as the most promising flame retardant, which can effectively reduce the burning rate and heat release rate of the combustion process, with excellent smoke suppression effect. Based on the relevant parameters obtained from the experimental results of phosphorus-doped graphene oxide, Simtec simulation is operated to demonstrate vertical combustion of thin fabric before and after flame-retardant treatment, and the results are consistent with the trend of the experimental results and suggest a magnifying effect of phosphorus-doped graphene oxide.

Dissociation of Misfit Dislocations in GeSi/{111}Si Interfaces

1993 ◽  
Vol 319 ◽  
Author(s):  
Frank Ernst
Keyword(s):  
Lattice Mismatch ◽  
Stacking Faults ◽  
Chemical Vapor ◽  
Interfacial Area ◽  
Dark Field ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Si Substrates ◽  
Weak Beam ◽  
Transmission Electron

AbstractThe accommodation of lattice mismatch is studied in Ge0.15Si0.85 layers grown epitaxially on {111}-oriented Si substrates by chemical vapor deposition (CVD) at 1100°C. Weak beam dark field microscopy reveals a regular misfit dislocation network, which resembles the honeycomb network of edge-type dislocations anticipated by the O-lattice theory. In contrast to the latter, however, the real network exhibits extended nodes where the misfit dislocations dissociate into misfit partial dislocations. Between the partials, high resolution transmission electron microscopy (HRTEM) reveals intrinsic and extrinsic stacking faults. Owing to the presence of these stacking faults, three different atomistic structures of the GeSi/Si interface coexist and compete for the interfacial area according to their energy. The observed configuration is shown to minimize the total energy of the interface.

Multispike Interactions in a Stochastic Model of Spike-Timing-Dependent Plasticity

2007 ◽  
Vol 19 (5) ◽  
pp. 1362-1399 ◽  
Author(s):  
Peter A. Appleby ◽  
Terry Elliott
Keyword(s):  
Stochastic Model ◽  
Ad Hoc ◽  
Detailed Examination ◽  
Spike Timing ◽  
Competitive Dynamics ◽  
Experimental Results ◽  
Spike Timing Dependent Plasticity ◽  
Dependent Plasticity ◽  
Natural Way ◽  
Exact Timing

Recently we presented a stochastic, ensemble-based model of spike-timing-dependent plasticity. In this model, single synapses do not exhibit plasticity depending on the exact timing of pre- and postsynaptic spikes, but spike-timing-dependent plasticity emerges only at the temporal or synaptic ensemble level. We showed that such a model reproduces a variety of experimental results in a natural way, without the introduction of various, ad hoc nonlinearities characteristic of some alternative models. Our previous study was restricted to an examination, analytically, of two-spike interactions, while higher-order, multispike interactions were only briefly examined numerically. Here we derive exact, analytical results for the general n-spike interaction functions in our model. Our results form the basis for a detailed examination, performed elsewhere, of the significant differences between these functions and the implications these differences have for the presence, or otherwise, of stable, competitive dynamics in our model.

THE PHOTOCHEMICAL DECOMPOSITION OF SODIUM AZIDE

1966 ◽  
Vol 44 (6) ◽  
pp. 703-709 ◽  
Author(s):  
P. W. M. Jacobs ◽  
A. R. Tariq Kureishy
Keyword(s):  
Ultraviolet Light ◽  
Sodium Azide ◽  
Reaction Mechanisms ◽  
Linear Growth ◽  
Experimental Results ◽  
Dislocation Network ◽  
Metallic Sodium ◽  
Photochemical Decomposition ◽  
Good Agreement

When sodium azide is irradiated with ultraviolet light the rate of photolysis at first decreases and then becomes constant. Two reaction mechanisms are involved: the first occurs only in salt which has not previously been irradiated, whereas the second requires the presence of metallic sodium. These two reactions are interpreted as the formation and linear growth of nuclei in the dislocation network of the salt and an equation developed from this model gives good agreement with the experimental results. Incorporation of Fe3+ ions in NaN3 leads to a greater number of nucleus-forming sites.

Diagnostics of Gold Laser Plasmas

1988 ◽  
Vol 102 ◽  
pp. 357-360
Author(s):  
J.C. Gauthier ◽  
J.P. Geindre ◽  
P. Monier ◽  
C. Chenais-Popovics ◽  
N. Tragin ◽  
...  
Keyword(s):  
Experimental Results ◽  
Pure Gold ◽  
Electronic Temperature ◽  
X Ray ◽  
Laser Plasmas ◽  
Collisional Radiative Model ◽  
Radiative Model

AbstractIn order to achieve a nickel-like X ray laser scheme we need a tool to determine the parameters which characterise the high-Z plasma. The aim of this work is to study gold laser plasmas and to compare experimental results to a collisional-radiative model which describes nickel-like ions. The electronic temperature and density are measured by the emission of an aluminium tracer. They are compared to the predictions of the nickel-like model for pure gold. The results show that the density and temperature can be estimated in a pure gold plasma.

Two Investigations into Grain Boundary Structure

1977 ◽  
Vol 35 ◽  
pp. 688-691
Author(s):  
P. Humble
Keyword(s):  
Grain Boundary ◽  
Dark Field ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Bright Field ◽  
Intrinsic Structure ◽  
Weak Beam ◽  
Grain Boundary Structure ◽  
Independent Information ◽  
Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

Observation of Phase Contrast Images in STEM and CTEM Modes by Using 100 kV Field Emission Electron Gun

1974 ◽  
Vol 32 ◽  
pp. 390-391
Author(s):  
Y. Harada ◽  
T. Goto ◽  
H. Koike ◽  
T. Someya
Keyword(s):  
Field Emission ◽  
Phase Contrast ◽  
Image Formation ◽  
Fresnel Diffraction ◽  
Experimental Results ◽  
Electron Gun ◽  
Scanning Microscopy ◽  
Emission Electron ◽  
Lattice Images

Since phase contrasts of STEM images, that is, Fresnel diffraction fringes or lattice images, manifest themselves in field emission scanning microscopy, the mechanism for image formation in the STEM mode has been investigated and compared with that in CTEM mode, resulting in the theory of reciprocity. It reveals that contrast in STEM images exhibits the same properties as contrast in CTEM images. However, it appears that the validity of the reciprocity theory, especially on the details of phase contrast, has not yet been fully proven by the experiments. In this work, we shall investigate the phase contrast images obtained in both the STEM and CTEM modes of a field emission microscope (100kV), and evaluate the validity of the reciprocity theory by comparing the experimental results.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

Weak Beam Imaging and Diffraction Studies of Stacking Faults in Silicon

1976 ◽  
Vol 34 ◽  
pp. 590-591
Author(s):  
T. Y. Tan ◽  
W. K. Tice
Keyword(s):  
Fast Neutron ◽  
Rapid Determination ◽  
Stacking Faults ◽  
Imaging Method ◽  
Large Reduction ◽  
Dislocation Loops ◽  
Fringe Spacing ◽  
Weak Beam ◽  
Kinematical Theory

In studying ion implanted semiconductors and fast neutron irradiated metals, the need for characterizing small dislocation loops having diameters of a few hundred angstrom units usually arises. The weak beam imaging method is a powerful technique for analyzing these loops. Because of the large reduction in stacking fault (SF) fringe spacing at large sg, this method allows for a rapid determination of whether the loop is faulted, and, hence, whether it is a perfect or a Frank partial loop. This method was first used by Bicknell to image small faulted loops in boron implanted silicon. He explained the fringe spacing by kinematical theory, i.e., ≃l/(Sg) in the fault fringe in depth oscillation. The fault image contrast formation mechanism is, however, really more complicated.

TEM Study of a Tilt Boundary in Hot-Pressed Silicon

1981 ◽  
Vol 39 ◽  
pp. 160-161
Author(s):  
C. B. Carter ◽  
J. Rose ◽  
D. G. Ast
Keyword(s):  
Electron Diffraction ◽  
Imaging Technique ◽  
Interface Structure ◽  
Large Area ◽  
Weak Beam ◽  
Lattice Fringe ◽  
Electron Diffraction Technique ◽  
Tilt Boundaries ◽  
Beam Technique ◽  
Twist Boundaries

The hot-pressing technique which has been successfully used to manufacture twist boundaries in silicon has now been used to form tilt boundaries in this material. In the present study, weak-beam imaging, lattice-fringe imaging and electron diffraction techniques have been combined to identify different features of the interface structure. The weak-beam technique gives an overall picture of the geometry of the boundary and in particular allows steps in the plane of the boundary which are normal to the dislocation lines to be identified. It also allows pockets of amorphous SiO2 remaining in the interface to be recognized. The lattice-fringe imaging technique allows the boundary plane parallel to the dislocation to be identified. Finally the electron diffraction technique allows the periodic structure of the boundary to be evaluated over a large area - this is particularly valuable when the dislocations are closely spaced - and can also provide information on the structural width of the interface.

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