Pulsed Laser Atom Probe Analysis of III-V Compound Semiconductor Epilayers.

1989 ◽  
Vol 160 ◽  
Author(s):  
Ross A. D. Mackenzie ◽  
J. Alex Liddle ◽  
Chris R. M. Grovenor ◽  
Alfred Cerezo
Keyword(s):  
Indium Phosphide ◽  
Pulsed Laser ◽  
Atom Probe ◽  
Miscibility Gap ◽  
Fine Scale ◽  
Quaternary Compound ◽  
Group Iii ◽  
Contrast Mechanism ◽  
Compositional Variations ◽  
20 Nm

AbstractThe pulsed laser atom probe has been used to characterise the fine scale chemistry of a range of III-V ternary and quaternary compound semiconductors (GaInAs, AlInAs, GaAlInAs) grown, using MOCVD techniques, on indium phosphide substrates. It has been observed that there are fine scale chemical fluctuations in some specimens on a scale of typically 10–20 nm. The fluctuations appear to be a result of localized clustering of the group III components in the epilayer. In quaternary material there is evidence for different degrees of clustering for different components. It is suggested that this compositional fluctuation is a consequence of clustering occuring above a miscibility gap. The existence of a TEM contrast mechanism inherent to the material has the effect of making TEM an unreliable indicator of fine scale compositional variations in these systems.

A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures

1985 ◽  
Vol 43 ◽  
pp. 70-71
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Low Temperature ◽  
Microstructural Characterization ◽  
Superlattice Reflection ◽  
High Volume ◽  
Atom Probe ◽  
Dark Field ◽  
Miscibility Gap ◽  
Second Phase ◽  
Two Phase ◽  
Probe Field

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.

PULSED-LASER ATOM-PROBE STUDY OF Al-GaAs INTERFACES

1986 ◽  
Vol 47 (C7) ◽  
pp. C7-303-C7-308
Author(s):  
O. NISHIKAWA ◽  
M. YANAGISAWA ◽  
M. NAGAI
Keyword(s):  
Pulsed Laser ◽  
Atom Probe

An atom probe tomography study of grain boundary segregation in nanocrystalline Ni-W

2005 ◽  
Vol 903 ◽  
Author(s):  
Andrew Detor ◽  
Michael K. Miller ◽  
Christopher A. Schuh
Keyword(s):  
Grain Boundary ◽  
Atom Probe Tomography ◽  
Boundary Segregation ◽  
Atom Probe ◽  
Solute Segregation ◽  
Grain Boundary Segregation ◽  
Distribution Analysis ◽  
Grain Sizes ◽  
Composition Fluctuations ◽  
20 Nm

AbstractAtom probe tomography is used to observe the solute distribution in electrodeposited nanocrystalline Ni-W alloys with three different grain sizes (3, 10, and 20 nm) and the results are compared with atomistic computer simulations. The presence of grain boundary segregation is confirmed by detailed analysis of composition fluctuations in both experimental and simulated structures, and its extent quantified by a frequency distribution analysis. In contrast to other nanocrystalline alloys, the present Ni-W alloys exhibit only a subtle amount of solute segregation to the intergranular regions. This finding is consistent with quantitative predictions for these alloys based upon a thermodynamic model of grain boundary segregation.

Nanoscale 3D Chemical Mapping by Spectroscopic Electron Tomography

2002 ◽  
Vol 738 ◽  
Author(s):  
Günter Möbus ◽  
Ron C. Doole ◽  
Beverley J. Inkson
Keyword(s):  
Materials Science ◽  
Electron Tomography ◽  
Region Of Interest ◽  
Atom Probe ◽  
Lattice Plane ◽  
Chemical Mapping ◽  
Bragg Scattering ◽  
Electron Spectroscopic Imaging ◽  
Contrast Mechanism ◽  
Data Volume

ABSTRACTElectron Tomography is shown to be applicable to problems of materials science if a contrast mechanism is used which provides a projection relationship for crystals not depending on lattice plane orientation. Energy filtered TEM (EFTEM) in its mode of electron spectroscopic imaging (ESI) and STEM-EDX-Mapping are, subject to limitations, suitable image formation techniques. The spectroscopic operation not only allows to overcome Bragg scattering artefacts, but offers the possibility of recording 4-dimensional data (volume and energy) of a region of interest, otherwise only known from NMR and XAS/XANES tomography at larger length-scales and from field-ion microscopy (atom probe) under restrictive conditions.

On the Field Evaporation Behavior of a Model Ni-Al-Cr Superalloy Studied by Picosecond Pulsed-Laser Atom-Probe Tomography

2008 ◽  
Vol 14 (6) ◽  
pp. 571-580 ◽  
Author(s):  
Yang Zhou ◽  
Christopher Booth-Morrison ◽  
David N. Seidman
Keyword(s):  
Atom Probe Tomography ◽  
Mass Spectra ◽  
Pulsed Laser ◽  
Picosecond Laser ◽  
Atom Probe ◽  
Resolving Power ◽  
Noise Levels ◽  
Thermally Activated ◽  
Mass Resolving Power

AbstractThe effects of varying the pulse energy of a picosecond laser used in the pulsed-laser atom-probe (PLAP) tomography of an as-quenched Ni-6.5 Al-9.5 Cr at.% alloy are assessed based on the quality of the mass spectra and the compositional accuracy of the technique. Compared to pulsed-voltage atom-probe tomography, PLAP tomography improves mass resolving power, decreases noise levels, and improves compositional accuracy. Experimental evidence suggests that Ni2+, Al2+, and Cr2+ ions are formed primarily by a thermally activated evaporation process, and not by post-ionization of the ions in the 1+ charge state. An analysis of the detected noise levels reveals that for properly chosen instrument parameters, there is no significant steady-state heating of the Ni-6.5 Al-9.5 Cr at.% tips during PLAP tomography.

Interfacial chemistry in an InAs/GaSb superlattice studied by pulsed laser atom probe tomography

2012 ◽  
Vol 100 (8) ◽  
pp. 083109 ◽  
Author(s):  
M. Müller ◽  
B. Gault ◽  
M. Field ◽  
G. J. Sullivan ◽  
G. D. W. Smith ◽  
...  
Keyword(s):  
Atom Probe Tomography ◽  
Pulsed Laser ◽  
Atom Probe ◽  
Interfacial Chemistry

Investigation of Performance-Influencing Factors in Pulsed Laser Atom Probe

2008 ◽  
Vol 14 (S2) ◽  
pp. 1238-1239 ◽  
Author(s):  
JH Bunton ◽  
JD Olson ◽  
DR Lenz ◽  
TF Kelly
Keyword(s):  
New Mexico ◽  
Influencing Factors ◽  
Pulsed Laser ◽  
Atom Probe ◽  
Performance Influencing Factors

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

scholarly journals Atomic Level Characterization of the Morphology of Phases in Chromindur Magnetic Alloys

1991 ◽  
Vol 232 ◽  
Author(s):  
M. K Miller ◽  
P. P. Camus ◽  
M. G. Hetherington
Keyword(s):  
Atom Probe ◽  
Heat Treatments ◽  
Miscibility Gap ◽  
Probe Field ◽  
Magnet Alloy ◽  
Two Phases ◽  
Isothermal Heat Treatments ◽  
Field Ion Microscope ◽  
Permanent Magnet Alloy

ABSTRACTThe atom probe field ion microscope has been used to characterize the morphology and determine the compositions of the iron-rich a and chromium-enriched α′ phases produced during isothermal and step cooled heat treatments in a Chromindur II ductile permanent magnet alloy. The good magnetic properties of this material are due to a combination of the composition of the two phases and the isolated nature and size of the ferromagnetic a phase. The morphology of the a phase is produced as a result of the shape of the miscibility gap and the step-cooled heat treatment and is distinctly different from that formed during isothermal heat treatments.

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