An Experimental Study of Step Dynamics under the Influence of Electromigration: Si(111)

1997 ◽  
Vol 11 (31) ◽  
pp. 3691-3702 ◽  
Author(s):  
J.-J. Métois ◽  
M. Audiffren
Keyword(s):  
Experimental Study ◽  
Electron Microscope ◽  
Surface Diffusion ◽  
Critical Frequency ◽  
Diffusion Field ◽  
Step Bunching ◽  
Step Motion ◽  
Different Temperatures ◽  
Step Step

The velocity of monoatomic step motion in the neighborhood of a bunch has been measured in situ using a UHV electron microscope. The width of step bunches at different temperatures and the intrinsic time that lead to step bunching have also been determined. Direct and alternating current were used to heat the Silicon(111) between 1000°C and 1300°C. The results show that the diffusion regime prevails. The asymmetry of the surface diffusion of adatoms is proved experimentally. It is consistent with the adatom electromigration effects. The surface diffusion field under the influence of an electric current can induce an attractive force between the steps. This force balances the step-step repulsive interactions (entropic and energetic) inside the bunch and stabilizes its width. The effective charge on the adatom has been estimated from the critical frequency of AC when the step bunching does not operate. It is around 0.001 electron.

The Etching of Silicon by Oxygen Observed by in situ Tem

1991 ◽  
Vol 222 ◽  
Author(s):  
Frances M. Ross ◽  
J. Murray Gibson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
In Situ Tem ◽  
Step Motion ◽  
Etching Mechanism ◽  
Transmission Electron ◽  
Macroscopic Parameters ◽  
Made In ◽  
Oxygen Etching

ABSTRACTWe describe observations made in situ in a modified UHV transmission electron microscope of the process of etching of the Si (111) surface by oxygen. Etching occurs by the motion of individual bilayer steps across the surface and by analysing the step motion we discuss the etching mechanism in the context of macroscopic parameters.

scholarly journals Some Deformation Micromechanisms in Ni-Based Superalloys Evidenced Using TEM In Situ Experiments

2011 ◽  
Vol 278 ◽  
pp. 90-95
Author(s):  
Florence Pettinari-Sturmel ◽  
Mustafa Benyoucef ◽  
Joël Douin ◽  
Pierre Caron ◽  
Didier Locq ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Quantitative Evaluation ◽  
Transmission Electron Microscope ◽  
Strengthening Effect ◽  
Transmission Electron ◽  
The Matrix ◽  
Different Temperatures

In situ straining of microsamples have been carried out at different temperatures in a transmission electron microscope (TEM) to provide information about the elementary micromechanisms, which control the deformation in Ni-based superalloys at the nano and microscopic scales. The obstacles to the propagation of the dislocations have been identified and quantified when possible. The strengthening effect in the -matrix channels and the shearing of ' precipitates have been chosen to illustrate some results deduced from moving dislocation analysis. A quantitative evaluation of the stresses acting on dislocations has been performed. The shearing process of the ' precipitates at 850°C has been precisely analysed.

Wandering and Bunching Instabilities of Steps Described By Nonlinear Evolution Equations

1998 ◽  
Vol 05 (03n04) ◽  
pp. 841-849 ◽  
Author(s):  
Makio Uwaha ◽  
Masahide Sato
Keyword(s):  
Electric Field ◽  
Critical Point ◽  
Surface Diffusion ◽  
Evolution Equations ◽  
Spatiotemporal Chaos ◽  
Nonlinear Evolution Equations ◽  
Diffusion Field ◽  
Step Motion ◽  
Lower Terrace ◽  
Step Density

We study wandering and bunching instabilities of steps in a surface diffusion field with a direct electric field applied perpendicular to the steps. The drift of adatoms induced by the electric field modifies the surface diffusion length in the upper terrace and that in the lower terrace. This asymmetry causes wandering instability of an isolated step when the drift is opposite to the step motion. Near the critical point the time evolution of a step obeys the Kuramoto–Sivashinsky equation, which gives rise to spatiotemporal chaos. The asymmetry also causes bunching instability of an array of repulsive straight steps. The instability near the critical point is an amplification of density large wavelength. The step density after the instability obeys the Benney equation, which shows a stable array of solitons corresponding to the formation of stable bunches.

Application of analytical electron microscopy to the study of partitioning of silicon in a 2 wt% Si eutectoid steel

1978 ◽  
Vol 36 (1) ◽  
pp. 616-617
Author(s):  
N. Ridley ◽  
S.A. Al-Salman ◽  
G.W. Lorimer
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Analytical Electron Microscopy ◽  
Eutectoid Steel ◽  
Minimum Diameter ◽  
Thin Foils ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Transformation Front

The application of the technique of analytical electron microscopy to the study of partitioning of Mn (1) and Cr (2) during the austenite-pearlite transformation in eutectoid steels has been described in previous papers. In both of these investigations, ‘in-situ’ analyses of individual cementite and ferrite plates in thin foils showed that the alloying elements partitioned preferentially to cementite at the transformation front at higher reaction temperatures. At lower temperatures partitioning did not occur and it was possible to identify a ‘no-partition’ temperature for each of the steels examined.In the present work partitioning during the pearlite transformation has been studied in a eutectoid steel containing 1.95 wt% Si. Measurements of pearlite interlamellar spacings showed, however, that except at the highest reaction temperatures the spacing would be too small to make the in-situ analysis of individual cementite plates possible, without interference from adjacent ferrite lamellae. The minimum diameter of the analysis probe on the instrument used, an EMMA-4 analytical electron microscope, was approximately 100 nm.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

In-situ electrical-resistivity measurements in the high-voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 68-69
Author(s):  
W. E. King
Keyword(s):  
Electrical Resistivity ◽  
Electron Microscope ◽  
High Voltage ◽  
Resistivity Measurements ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Wide Range ◽  
Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

A TEM study of the microstructure of avian eggshells

1992 ◽  
Vol 50 (2) ◽  
pp. 1102-1103
Author(s):  
S. Q. Xiao ◽  
S. Baden ◽  
A. H. Heuer
Keyword(s):  
Electron Microscope ◽  
Calcium Carbonate ◽  
Nucleation And Growth ◽  
Growth Mechanisms ◽  
Shell Surface ◽  
Thin Sections ◽  
Polycrystalline Metals ◽  
Transmission Electron ◽  
Nucleation And Growth Mechanisms

The avian eggshell is one of the most rapidly mineralizing biological systems known. In situ, 5g of calcium carbonate are crystallized in less than 20 hrs to fabricate the shell. Although there have been much work about the formation of eggshells, controversy about the nucleation and growth mechanisms of the calcite crystals, and their texture in the eggshell, still remain unclear. In this report the microstructure and microchemistry of avian eggshells have been analyzed using transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS).Fresh white and dry brown eggshells were broken and fixed in Karnosky's fixative (kaltitanden) for 2 hrs, then rinsed in distilled H2O. Small speckles of the eggshells were embedded in Spurr medium and thin sections were made ultramicrotome.The crystalline part of eggshells are composed of many small plate-like calcite grains, whose plate normals are approximately parallel to the shell surface. The sizes of the grains are about 0.3×0.3×1 μm3 (Fig.l). These grains are not as closely packed as man-made polycrystalline metals and ceramics, and small gaps between adjacent grains are visible indicating the absence of conventional grain boundaries.

In situ TEM observations of melting in nanosized eutectic Pb-Cd inclusions embedded in Al

1996 ◽  
Vol 54 ◽  
pp. 986-987
Author(s):  
S. Hagège ◽  
U. Dahmen ◽  
E. Johnson ◽  
A. Johansen ◽  
V.S. Tuboltsev
Keyword(s):  
Electron Microscope ◽  
Melt Spinning ◽  
Ternary Alloys ◽  
Solid Matrix ◽  
Eutectic System ◽  
In Situ Tem ◽  
In Situ Observation ◽  
Orientation Relationships ◽  
Transmission Electron

Small particles of a low-melting phase embedded in a solid matrix with a higher melting point offer the possibility of studying the mechanisms of melting and solidification directly by in-situ observation in a transmission electron microscope. Previous studies of Pb, Cd and other low-melting inclusions embedded in an Al matrix have shown well-defined orientation relationships, strongly faceted shapes, and an unusual size-dependent superheating before melting.[e.g. 1,2].In the present study we have examined the shapes and thermal behavior of eutectic Pb-Cd inclusions in Al. Pb and Cd form a simple eutectic system with each other, but both elements are insoluble in solid Al. Ternary alloys of Al (Pb,Cd) were prepared from high purity elements by melt spinning or by sequential ion implantation of the two alloying additions to achieve a total alloying addition of up to lat%. TEM observations were made using a heating stage in a 200kV electron microscope equipped with a video system for recording dynamic behavior.

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