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 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.

Fabrication and characterization - by High Resolution Electron Microscopy and atom probe microanalysis - of Co-based metallic multilayer films

1990 ◽  
Vol 48 (4) ◽  
pp. 772-773
Author(s):  
Amanda K. Petford-Long ◽  
A. Cerezo ◽  
M.G. Hetherington
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Atom Probe ◽  
Multilayer Films ◽  
Interface Roughness ◽  
Probe Field ◽  
Resolution Electron ◽  
Potential Applications ◽  
Field Ion Microscope

The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to the development of materials with unique properties not found in bulk materials. The properties of interest depend critically on the structure and composition of the films, with the interfacial regions between the layers being of particular importance. There are a number of magnetic MLF systems based on Co, several of which have potential applications as perpendicular magnetic (e.g Co/Cr) or magneto-optic (e.g. Co/Pt) recording media. Of particular concern are the effects of parameters such as crystallographic texture and interface roughness, which are determined by the fabrication conditions, on magnetic properties and structure.In this study we have fabricated Co-based MLF by UHV thermal evaporation in the prechamber of an atom probe field-ion microscope (AP). The multilayers were deposited simultaneously onto cobalt field-ion specimens (for AP and position-sensitive atom probe (POSAP) microanalysis without exposure to atmosphere) and onto the flat (001) surface of oxidised silicon wafers (for subsequent study in cross-section using high-resolution electron microscopy (HREM) in a JEOL 4000EX. Deposi-tion was from W filaments loaded with material in the form of wire (Co, Fe, Ni, Pt and Au) or flakes (Cr). The base pressure in the chamber was around 8×10−8 torr during deposition with a typical deposition rate of 0.05 - 0.2nm/s.

scholarly journals The MiMeS project: overview and current status

2010 ◽  
Vol 6 (S272) ◽  
pp. 118-123 ◽  
Author(s):  
Gregg A. Wade ◽  
Evelyne Alecian ◽  
David A. Bohlender ◽  
Jean-Claude Bouret ◽  
David H. Cohen ◽  
...  
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Massive Stars ◽  
Data Modeling ◽  
Current Status ◽  
Individual Stars ◽  
Related Theory ◽  
The Status ◽  
Very High

AbstractThe Magnetism in Massive Stars (MiMeS) Project is a consensus collaboration among many of the foremost international researchers of the physics of hot, massive stars, with the basic aim of understanding the origin, evolution and impact of magnetic fields in these objects. At the time of writing, MiMeS Large Programs have acquired over 950 high-resolution polarised spectra of about 150 individual stars with spectral types from B5-O4, discovering new magnetic fields in a dozen hot, massive stars. The quality of this spectral and magnetic matériel is very high, and the Collaboration is keen to connect with colleagues capable of exploiting the data in new or unforeseen ways. In this paper we review the structure of the MiMeS observing programs and report the status of observations, data modeling and development of related theory.

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).

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.

scholarly journals Very-high-resolution mapping of river-immersed topography by remote sensing

2008 ◽  
Vol 32 (4) ◽  
pp. 403-419 ◽  
Author(s):  
Denis Feurer ◽  
Jean-Stéphane Bailly ◽  
Christian Puech ◽  
Yann Le Coarer ◽  
Alain A. Viau
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Large Scale ◽  
Aerial Image ◽  
Depth Measurement ◽  
Very High Spatial Resolution ◽  
Remote Sensing Techniques ◽  
Logarithmic Relationship ◽  
Ground Penetrating ◽  
Very High

Remote sensing has been used to map river bathymetry for several decades. Non-contact methods are necessary in several cases: inaccessible rivers, large-scale depth mapping, very shallow rivers. The remote sensing techniques used for river bathymetry are reviewed. Frequently, these techniques have been developed for marine environment and have then been transposed to riverine environments. These techniques can be divided into two types: active remote sensing, such as ground penetrating radar and bathymetric lidar; or passive remote sensing, such as through-water photogrammetry and radiometric models. This last technique — which consists of finding a logarithmic relationship between river depth and image values — appears to be the most used. Fewer references exist for the other techniques, but lidar is an emerging technique. For each depth measurement method, we detail the physical principles and then a review of the results obtained in the field. This review shows a lack of data for very shallow rivers, where a very high spatial resolution is needed. Moreover, the cost related to aerial image acquisition is often huge. Hence we propose an application of two techniques, radiometric models and through-water photogrammetry, with very- high-resolution passive optical imagery, light platforms, and off-the-shelf cameras. We show that, in the case of the radiometric models, measurement is possible with a spatial filtering of about 1 m and a homogeneous river bottom. In contrast, with through-water photogrammetry, fine ground resolution and bottom textures are necessary.

Atom-Probe Microanalysis of Metallic Nanostructured Materials

1992 ◽  
Vol 286 ◽  
Author(s):  
Ross A.D. Mackenzie ◽  
Alfred Cerezo ◽  
James S. Conyers ◽  
Amanda K. Petford-Long ◽  
Sybren J. Subrandu ◽  
...  
Keyword(s):  
Nanostructured Materials ◽  
Thermal Evaporation ◽  
Atom Probe ◽  
Sputter Deposition ◽  
Dual Phase ◽  
Metallic Materials ◽  
Nanocrystalline Films ◽  
Thermal Evaporator ◽  
Position Sensitive

ABSTRACTAtom-probe techniques have been used to characterise nanostructured metallic materials prepared by thermal evaporation and by sputtering. Multilayer samples of Fe-Cr have been prepared by sputter deposition and analysed using the Oxford position-sensitive atom probe. This has made it possible to observe the quality of interfaces in the material, and also accurately determine local compositions at each layer within the multilayer stack. Preliminary experiments aimed at producing dual phase nanocrystalline films by thermal evaporator deposition are also reported.

scholarly journals Morphological and Structural Characterization of the Spinodal Decomposition of FE-CR Alloys.

1990 ◽  
Vol 186 ◽  
Author(s):  
A. Cerezo ◽  
M.G. Hetherington ◽  
J.M. Hyde ◽  
M.K. Miller
Keyword(s):  
High Resolution ◽  
Spinodal Decomposition ◽  
Structural Characterization ◽  
Atom Probe ◽  
3 Dimensional ◽  
Position Sensitive

AbstractThe position sensitive atom-probe (POSAP) is capable of extremely high resolution (subnanometer) microanalysis. Its 3-dimensional capabilities are unique and offer a new opportunity to study the topology and structure of materials. This paper is an initial overview of the new types of parameters and analysis that this technique makes possible.

A `static' high-resolution X-ray diffractometer

2005 ◽  
Vol 38 (1) ◽  
pp. 62-68 ◽  
Author(s):  
Paul F. Fewster
Keyword(s):  
High Resolution ◽  
Real Space ◽  
Quality Data ◽  
High Angular Resolution ◽  
X Ray ◽  
Spectral Contribution ◽  
State Position ◽  
Position Sensitive ◽  
Good Quality Data

This new diffractometer utilizes angular and spatial aspects to create a motionless high-resolution X-ray diffractometer that will collect good quality data within one second. The instrument is configured specifically for different materials, but when set the sample to be analysed need only be placed approximately on a mount prior to data collection. By appropriate use of reciprocal space, the wavelength dispersion is limited, and by using real space the spatial resolution can create data of high angular resolution. The components of the diffractometer rely on a solid-state position-sensitive detector. The quality of the scattering profile is found to be essentially independent of the exact orientation of the sample. The scattering profile is simulated to include the spectral contribution and all the components of the diffractometer. The experimental profiles and the resulting model, through simulation, are compared with those from a conventional high-resolution diffractometer for an InGaAs structure and a SiGe structure.

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