The position-sensitive atom probe: Reconstruction of the atomic chemistry of solids in 3-dimensions (summary)

1991 ◽  
Vol 104 (1-6) ◽  
pp. 401-404 ◽  
Author(s):  
Alfred Cerezo ◽  
George D. W. Smith
Keyword(s):  
Atom Probe ◽  
Position Sensitive

Characterisation of multilayer materials using a position-sensitive atom probe

1990 ◽  
Vol 48 (4) ◽  
pp. 624-625
Author(s):  
RAD Mackenzie ◽  
G D W Smith ◽  
A. Cerezo ◽  
J A Liddle ◽  
CRM Grovenor ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Spatial Information ◽  
Chemical Vapour ◽  
Atom Probe ◽  
Organic Chemical ◽  
Growth Stages ◽  
Multiple Quantum ◽  
Quartz Wool ◽  
Position Sensitive

The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. The first set of wells examined were prepared in a conventional reactor to which a quartz wool baffle had been added to promote gas intermixing. The effect of this was to hold a volume of gas within the chamber between growth stages, leading to a structure where the wells had a composition of GalnAsP lattice matched to the InP barriers, and where the interfaces were very indistinct. A POSAP image showing a well in this sample is shown in figure 1. The second set of wells were grown in the same reactor but with the quartz wool baffle removed. This set of wells were much better defined, as can be seen in figure 2, and the wells were much closer to the intended composition, but still with measurable levels of phosphorus. The final set of wells examined were prepared in a reactor where the design had the effect of minimizing the recirculating volume of gas. In this case there was again further improvement in the well quality. It also appears that the left hand side of the well in figure 2 is more abrupt than the right hand side, indicating that the switchover at this interface from barrier to well growth is more abrupt than the switchover at the other interface.

Lateral and depth scale calibration of the position sensitive atom probe

1994 ◽  
Vol 76-77 ◽  
pp. 382-391 ◽  
Author(s):  
J.M. Hyde ◽  
A. Cerezo ◽  
R.P. Setna ◽  
P.J. Warren ◽  
G.D.W. Smith
Keyword(s):  
Atom Probe ◽  
Depth Scale ◽  
Scale Calibration ◽  
Position Sensitive

Application of position sensitive atom probe to the study of the microchemistry and morphology of quantum well interfaces

1989 ◽  
Vol 54 (16) ◽  
pp. 1555-1557 ◽  
Author(s):  
J. A. Liddle ◽  
A. G. Norman ◽  
A. Cerezo ◽  
C. R. M. Grovenor
Keyword(s):  
Quantum Well ◽  
Atom Probe ◽  
Position Sensitive

Spatial and Compositional Biases Introduced by Position Sensitive Detection Systems in APT: A Simulation Approach

2019 ◽  
Vol 25 (2) ◽  
pp. 418-424 ◽  
Author(s):  
C. Bacchi ◽  
G. Da Costa ◽  
F. Vurpillot
Keyword(s):  
Detection System ◽  
Atom Probe ◽  
Signal Loss ◽  
Loss Mechanism ◽  
Multiple Events ◽  
Detection Systems ◽  
Statistical Correction ◽  
Position Sensitive ◽  
Position Sensitive Detectors ◽  
The Impact

AbstractDue to the low capacity of contemporary position-sensitive detectors in atom probe tomography (APT) to detect multiple events, material analyses that exhibit high numbers of multiple events are the most subject to compositional biases. To solve this limitation, some researchers have developed statistical correction algorithms. However, those algorithms are only efficient when one is confronted with homogeneous materials having nearly the same evaporation field between elements. Therefore, dealing with more complex materials must be accompanied by a better understanding of the signal loss mechanism during APT experiments. By modeling the evaporation mechanism and the whole APT detection system, it may be possible to predict compositional and spatial biases induced by the detection system. This paper introduces a systematic study of the impact of the APT detection system on material analysis through the development of a simulation tool.

Ultra-high resolution chemical analysis by field-ion atom probe/position sensitive atom probe techniques

1991 ◽  
Vol 49 ◽  
pp. 486-487
Author(s):  
C.R.M. Grovenor ◽  
A. Cerezo ◽  
J.A. Liddle ◽  
R.A.D. Mackenzie ◽  
M.G. Hetherington ◽  
...  
Keyword(s):  
High Resolution ◽  
Sample Surface ◽  
Atom Probe ◽  
Three Dimensions ◽  
Very High Spatial Resolution ◽  
Chemical Profiles ◽  
Position Sensitive ◽  
Field Ion Microscope ◽  
Very High

The use of field ion microscopy based techniques in the study of the structure and chemistry of metallic and semiconducting materials with very high resolution is now well documented. The particular features of these techniques which result in the achievement of very high spatial resolution in images and chemical profiles are; the intrinsic magnification in a conventional field ion microscope of at least 106, the plane-by-plane desorption characteristic of field evaporation processes, and the excellent chemical specificity in a modern atom probe. In addition, we have developed in Oxford a new detector system for field ion based equipment in which both the chemical identity of evaporated ions and the position on the sample surface from which they were evaporated can be established. This allows the reconstruction of the evaporated volume in three dimensions, and this technique has been christened the Position Sensitive Atom Probe, POSAP. This abstract presents the results of two typical experiments illustrating the very high quality of the chemical data that can be obtained in both conventional atom probe and POSAP facilities.

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).

Application of a Position Sensitive Atom Probe to the Analysis of the Chemistry and Morphology of Multi-Quantum Well Interfaces

1989 ◽  
Vol 139 ◽  
Author(s):  
Alfred Cerezo ◽  
J. Alex Liddle ◽  
Chris R.M. Grovenor ◽  
Andrew G. Norman ◽  
George D.W. Smith
Keyword(s):  
Quantum Well ◽  
Atom Probe ◽  
Position Sensitive ◽  
Multi Quantum Well

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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