Characterisation of Ultrafine Microstructures Using a Position-Sensitive Atom Probe (POSAP)

1988 ◽  
Vol 132 ◽  
Author(s):  
Alfred Cerezo ◽  
Chris R. M. Grovenor ◽  
Mark G. Hetherington ◽  
Barbara A. Shollock ◽  
George D. W. Smith
Keyword(s):  
Solid Angle ◽  
Three Dimensional ◽  
Atom Probe ◽  
Field Evaporation ◽  
Sensitive Detector ◽  
Substantial Fraction ◽  
New Instrument ◽  
New Development ◽  
Position Sensitive ◽  
Permanent Magnet Materials

ABSTRACTA new development in the experimental techniques of atom probe microanalysis is described, which involves the use of a position sensitive detector system. This detector subtends a large solid angle (∼20°) at the specimen, and therefore permits the collection of ions from a substantial fraction of the whole surface area of the emitter. Progressive pulsed field evaporation leads to the construction of a three-dimensional map of the atomic chemistry of the specimen. The new instrument is ideally suited to the investigation of complex, ultrafine microstructures. Applications to the study of age-hardened aluminium alloys and Alnico permanent magnet materials are described.

Three Dimensional materials characterisation at ultrahigh resolution using a position-sensitive atom probe

1990 ◽  
Vol 48 (4) ◽  
pp. 408-409
Author(s):  
R A D Mackenzie ◽  
G D W Smith ◽  
A Cerezo ◽  
T J Godfrey ◽  
J.E. Brown
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Spatial Information ◽  
Three Dimensional ◽  
Atom Probe ◽  
Sensitive Detector ◽  
Channel Plate ◽  
Position Sensitive ◽  
20 Nm ◽  
Very High

The conventional atom probe field ion microscope permits very high resolution chemical information to be determined with a lateral spatial resolution of typically 2 nm. This spatial resolution is determined by the need to define the analysis area using an aperture. A recent development, the position sensitive atom probe (POSAP), has largely removed this limitation. In a conventional atom probe the ions passing through the aperture, which have come from a circular area of the order of 2 nm in diameter, travel along a long flight path where the mass to charge ratios are determined with high precision. In the position sensitive atom probe the aperture assembly, long flight tube and ion detector (a channel plate) are replaced with a position sensitive detector held at a known distance from the specimen surface. This detector consists of two parts, a channel plate component which permits the flight times (and hence mass to charge ratios) to be determined, and a wedge and strip anode which permits the position of the incoming ion to be calculated. This arrival position corresponds directly to the position on the specimen from which the ion came. The total field of view of the POSAP is a disc approximately 20 nm in diameter. With a conventional atom probe the data acquired during the evaporation sequence can be considered as a core extracted from the specimen, where the average composition as a function of depth is known. The position sensitive atom probe permits us to record data from a much wider core (20 nm rather than 2 nm in diameter), and also to retain the spatial information within the core. As the evaporation proceeds the two dimensional information yielded by the position sensitive detector builds up into a three dimensional block of data. We have, therefore, both chemical and spatial information in three dimensions at very high resolution from the sampled volume of material.

scholarly journals Automated Atom-By-Atom Three-Dimensional (3D) Reconstruction of Field Ion Microscopy Data

2017 ◽  
Vol 23 (2) ◽  
pp. 255-268 ◽  
Author(s):  
Michal Dagan ◽  
Baptiste Gault ◽  
George D. W. Smith ◽  
Paul A. J. Bagot ◽  
Michael P. Moody
Keyword(s):  
Three Dimensional ◽  
Reconstruction Algorithm ◽  
Automated Analysis ◽  
Atom Probe ◽  
Crystal Defects ◽  
Steel Matrix ◽  
Field Evaporation ◽  
Field Ion Microscopy ◽  
Ion Microscopy ◽  
Microscopy Data

AbstractAn automated procedure has been developed for the reconstruction of field ion microscopy (FIM) data that maintains its atomistic nature. FIM characterizes individual atoms on the specimen’s surface, evolving subject to field evaporation, in a series of two-dimensional (2D) images. Its unique spatial resolution enables direct imaging of crystal defects as small as single vacancies. To fully exploit FIM’s potential, automated analysis tools are required. The reconstruction algorithm developed here relies on minimal assumptions and is sensitive to atomic coordinates of all imaged atoms. It tracks the atoms across a sequence of images, allocating each to its respective crystallographic plane. The result is a highly accurate 3D lattice-resolved reconstruction. The procedure is applied to over 2000 tungsten atoms, including ion-implanted planes. The approach is further adapted to analyze carbides in a steel matrix, demonstrating its applicability to a range of materials. A vast amount of information is collected during the experiment that can underpin advanced analyses such as automated detection of “out of sequence” events, subangstrom surface displacements and defects effects on neighboring atoms. These analyses have the potential to reveal new insights into the field evaporation process and contribute to improving accuracy and scope of 3D FIM and atom probe characterization.

Temperature-gradient analyzers for non-resonant inelastic X-ray scattering

2021 ◽  
Vol 28 (3) ◽  
Author(s):  
Daisuke Ishikawa ◽  
Alfred Q. R. Baron
Keyword(s):  
Temperature Gradient ◽  
Solid Angle ◽  
Dispersion Compensation ◽  
Full Width ◽  
Half Maximum ◽  
Sensitive Detector ◽  
X Ray ◽  
X Ray Scattering ◽  
Position Sensitive ◽  
And Performance

The detailed fabrication and performance of the temperature-gradient analyzers that were simulated by Ishikawa & Baron [(2010). J. Synchrotron Rad. 17, 12–24] are described and extended to include both quadratic and 2D gradients. The application of a temperature gradient compensates for geometric contributions to the energy resolution while allowing collection of a large solid angle, ∼50 mrad × 50 mrad, of scattered radiation. In particular, when operating relatively close to backscattering, π/2 − θB = 1.58 mrad, the application of a gradient of 1.32 K per 80 mm improves the measured total resolution from 60 to 25 meV at the full width at half-maximum, while when operating further from backscattering, π/2 − θB = 6.56 mrad, improvement from 330 to 32 meV is observed using a combination of a gradient of 6.2 K per 80 mm and dispersion compensation with a position-sensitive detector. In both cases, the operating energy was 15.8 keV and the incident bandwidth was 22 meV. Notably, the use of a temperature gradient allows a relatively large clearance at the sample, permitting installation of more complicated sample environments.

Laser-Assisted Field Evaporation of (R = Gd, Sm) High-Temperature Superconducting Coated Conductors

2021 ◽  
pp. 1-18
Author(s):  
Jesse D. Smith ◽  
Jeong Huh ◽  
Adam Shelton ◽  
Richard F. Reidy ◽  
Marcus L. Young
Keyword(s):  
High Temperature ◽  
High Temperature Superconductors ◽  
Compositional Analysis ◽  
Atom Probe ◽  
Fracture Probability ◽  
Coated Conductors ◽  
Field Evaporation ◽  
Laser Absorption ◽  
New Instrument ◽  
New Perspective

In the field of high-temperature superconductors, atom probe tomography is a relatively new instrument, with the ability to provide a new perspective on the 3D nanoscale microstructure. However, field evaporation of nonmetallic materials is fraught with unique challenges that matter little in the world of metallic evaporation. In this study, we review the laser absorption, correlated evaporation, molecular dissociation, and the crystallographic effects on the field evaporation of 800-m ${\rm RB}{\rm a}_ 2{\rm C}{\rm u}_ 3{\rm O}_{ 7-{\rm \delta }}$ (R = Gd, Sm) coated conductor tapes deposited by Reactive Co-Evaporation Cyclic Deposition and Reaction (RCE-CDR). Ultraviolet 355 nm laser pulsing was found to have a substantial beneficial effect on minimizing the fracture probability compared with 532 nm illumination, especially when evaporating insulating oxide precipitates. This, in turn, allows for the 3D compositional analysis of defects such as flux pinning centers introduced by precipitation and doping. As a result, evidence for the precipitation of nanoscale ${\rm G}{\rm d}_ 2{\rm C}{\rm u}_ 2{\rm O}_ 5$ is discussed. The effect of crystallographic orientation is studied, where [001] aligned evaporation is found to develop compositional aberrations.

scholarly journals Spatial Resolution in the Atom Probe Field Ion Microscope

1997 ◽  
Vol 3 (S2) ◽  
pp. 1189-1190
Author(s):  
M. K. Miller
Keyword(s):  
Spatial Resolution ◽  
Atom Probe ◽  
Single Atom ◽  
Field Evaporation ◽  
Sensitive Detector ◽  
Probe Field ◽  
3 Dimensional ◽  
Number Of Factors ◽  
The Individual ◽  
Field Ion Microscope

The atom probe field ion microscope can resolve and identify individual atoms. This ability is demonstrated in a pair of field ion micrographs of an Ni3Al specimen, Fig. 1, in which the individual atoms on the close packed (111) plane are clearly resolved. Comparison of these two micrographs reveals that an individual atom was field evaporated between the micrographs. Due to the hemispherical nature of the specimen, the ability to resolve this two dimensional atomic arrangement is only possible on low index plane facets. The spatial resolution in field ion images is determined by a number of factors including specimen temperature, material, microstructural features, specimen geometry, and crystallographic location.The spatial resolution of the data obtained in atom probe and 3 dimensional atom probe compositional analyses can be evaluated with the use of field evaporation or field desorption images. The field evaporation images are formed from the surface atoms with the use of a single atom sensitive detector whereas the field ion image is formed from the projection of a continuous supply of ionized image gas atoms.

Three-dimensional reconstruction of atomic-scale composition with the position-sensitive atom probe

1992 ◽  
Vol 50 (2) ◽  
pp. 1478-1479
Author(s):  
G.D.W. Smith ◽  
A. Cerezo ◽  
C.R.M. Grovenor ◽  
T.J. Godfrey ◽  
R.P. Setna
Keyword(s):  
Mass Spectrometer ◽  
Three Dimensional ◽  
Atom Probe ◽  
Atomic Scale ◽  
Single Atom ◽  
Small Aperture ◽  
Dimensional Reconstruction ◽  
Position Sensitive ◽  
Atom Level ◽  
Scale Composition

The combination of a field ion microscope with a time-of-flight mass spectrometer provides the capability for chemical microanalysis at the single atom level. Such an instrument is termed an Atom Probe. Conventionally, the connection between the microscope and the mass spectrometer is made via a small aperture hole in the imaging screen. This defines a region on the specimen, typically about 2nm across, from which the analysis is obtained. The disadvantage of this arrangement is that other regions of the specimen cannot be examined, as ions from all but the selected area strike the image screen and therefore do not pass into the mass spectrometer. In order to overcome this problem, we have developed a version of the Atom Probe which incorporates a wide-angle position sensitive detector system. This instrument, which we have termed the POSAP, is shown schematically in figure 1. Typically, the field of view in this instrument is about 20nm across. The number of ions collected per atom layer removed from the specimen surface is therefore approximately 5,000.

Prospects for compositional imaging with the atom probe microscope

1992 ◽  
Vol 50 (2) ◽  
pp. 1616-1617
Author(s):  
T. F. Kelly ◽  
P. P. Camus ◽  
J. J. McCarthy ◽  
D. J. Larson ◽  
L. M. Holzman ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Compositional Analysis ◽  
Atom Probe ◽  
Atomic Scale ◽  
Probe Field ◽  
Acquisition Rate ◽  
3D Data ◽  
Probe Microscope ◽  
Position Sensitive ◽  
Field Ion Microscope

For the purposes of analytical characterization on the atomic scale, the ultimate instrument would identify every atom in a sample and determine its position with atomic-scale resolution. The recently developed positionsensitive atom probe (POSAP) comes as close as yet possible to this goal. This is the only experimental technique which can analyze the three-dimensional (3D) composition of a sample on a sub-nanometer scale.By adding a position-sensitive detector (PSD) to a conventional atom probe/field ion microscope, a 3D data structure with position-correlated compositional analysis is acquired. The 3D data are stored on a computer and may be examined for structural and compositional information at an atomic level. Note that, because it uses time-of-flight mass spectroscopy, all elements and their isotopes are detected in this way with equal proficiency. Usually, the evaporation rate is mediated by pulsing the field on the specimen. This approach, however, severely limits the data acquisition rate (about 1 atom per second) and mass resolution (about 1 part in 30).

scholarly journals Study on the Field Evaporation in the Laser-assisted Three-dimensional Atom Probe Based on the Thermal Diffusivity

2014 ◽  
Vol 63 (10) ◽  
pp. 809-815 ◽  
Author(s):  
Takahiro ASAKA ◽  
Bunbunoshin TOMIYASU ◽  
Masato MORITA ◽  
Tetsuo TERAKAWA ◽  
Masanori OWARI
Keyword(s):  
Thermal Diffusivity ◽  
Three Dimensional ◽  
Atom Probe ◽  
Field Evaporation

The Position-Sensitive Atom Probe - A New Dimension In Atom Probe Analysis

1998 ◽  
Vol 4 (S2) ◽  
pp. 76-77
Author(s):  
A. Cerezo ◽  
P.J. Warren ◽  
G.D.W. Smith
Keyword(s):  
Atom Probe ◽  
High Magnification ◽  
Field Evaporation ◽  
3D Image ◽  
3 Dimensional ◽  
Single Atoms ◽  
Original Surface ◽  
Position Sensitive ◽  
Field Ion Microscope ◽  
The Ideal

A possible description of the ideal microscope would be an instrument which was able to reconstruct, with atomic resolution and in 3 dimensions, both the position and the chemical identity of atoms in a material. The 3-dimensional atom probe (3DAP) is the technique which comes closest to this goal.The position-sensitive atom probe (PoSAP) was the first 3DAP. In the PoSAP, the high magnification of the field-ion microscope is combined with the time-of-flight mass spectroscopy of the atom probe, and position-sensitive detection based on a wedge-and-strip anode, Fig.1. This combination allows the chemical identity and the original surface position to be determined for single atoms removed from a field-ion specimen by pulsed field evaporation. Continued field evaporation and analysis builds up a 3D image of the distribution of all the atomic species originally present in the material, Fig. 2.

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