Atom Probe Microscopy and Materials Science

Gault, Baptiste; Moody, Michael P.; Cairney, Julie M.; Ringer, Simon P.

doi:10.1007/978-1-4614-3436-8_9

Cited by 46 publications

(76 citation statements)

References 95 publications

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“…Mass resolving power (m/Dm), where m is the mass-to-charge state ratio at the apex of a particular peak and Dm is the full-width at a specific ratio of the peak maximum, is used to measure how well ion peaks can be differentiated from one another in a mass spectrum [15,46]. A greater mass resolving power enables more accurate peak identification because it reduces the chance of peak overlap, increasing chemical sensitivity.…”

Section: Mass Resolving Powermentioning

confidence: 99%

“…Therefore, evaporation behavior must be optimized in order to obtain accurate chemistries from APT [15]. This paper presents a systematic study on the effect of sample temperature, detection rate, and laser energy on the chemical response of UO 2 in order to avoid the presence of artifact-induced inhomogeneities.…”

Section: Introductionmentioning

confidence: 99%

“…Using this information, the sample tip is computationally reconstructed for in-depth analysis. A pulsed electric field is the primary method for extraction of surface ions for electrically conductive materials, but materials with poor electrical conductivity, such as oxides, require a pulsed laser to assist in the removal of surface ions by thermal excitation [15]. Although recent investigations have explored the physical mechanisms of evaporation, questions still remain regarding the sample and laser interactions and the mechanisms that assist in ion evaporation in oxides [16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

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Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

Valderrama

Henderson

Gan

et al. 2015

Journal of Nuclear Materials

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Section: Mass Resolving Powermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

Valderrama

Henderson

Gan

et al. 2015

Journal of Nuclear Materials

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“…We have employed a commercially available small hand-held Tesla coil to successfully improve or restore the performance of local electrodes (LEs) used in atom-probe tomography (APT [2]). The local-electrode atom-probe (LEAP) design [3] is advantageous in terms of specimen throughput and flexibility with specimen preparation [3].…”

mentioning

confidence: 99%

Improving Local Electrode Performance by Tesla Coil Electric Discharges

2017

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A Tesla coil generates high-voltage high-frequency low-current electric arcing [1]. We have employed a commercially available small hand-held Tesla coil to successfully improve or restore the performance of local electrodes (LEs) used in atom-probe tomography (APT [2]). The local-electrode atom-probe (LEAP) design [3] is advantageous in terms of specimen throughput and flexibility with specimen preparation [3]. The LEs, however, deteriorate with usage, resulting in excessive noise from electron field emission that limits data quality, voltage range, and the field-of-view accessible for APT analysis. Replacing a LE can carry significant cost and efforts have been undertaken to understand failure modes [4] and restoring LEs, e.g. by plasma cleaning [5].The breakdown voltage of a LE in vacuum can be tested easily in a LEAP with the so-called "flat-test" where a polished clean conductive flat surface is placed opposite to the electrode [5,6] and the voltage increased until electrical breakdown by electron field emission occurs. We placed the flat surface at ~100 µm or half the distance to where the flat substrate of a microtip array sample would be located, increasing the electric field by approximately a factor of 2 (or 4 for needle shaped so-called "wire tips") and causing electron emission from the LE to begin at about 50% relative to the voltage for breakdown during a regular APT analysis. We categorized LE performance determined with the flat test in terms of electron emission beginning at ~5kV ("usable"), above 7 kV ("good") or above 11 kV ("like new") in reference to voltage limits of 10kV, 14 kV, or better for APT analyses with microtip array specimens.We tested LE performance and restoration with the Tesla coil in a multi-user laboratory environment with many different types of samples, including metallic, ceramic, and semiconducting materials, nanowires and nanoparticles, and biominerals, providing a wide-ranging test bed for LE restoration after deterioration from general usage. To restore a deteriorated LE, we activated the Tesla coil by arcing against the surface of a block holding the LEs, Fig. 1, in air, and subsequently directed the arc to the active part (top cone) of the LEs, hitting each LE for 5-10 seconds directly with the discharge. Longer exposure was not found to yield any further improvements. Using the breakdown voltage of air, ~3 kV/mm [7], we estimated applied voltages of about 15-50 kV from the length of the arcs, 5-20 mm. Ten different local electrodes were treated with the Tesla coil during a four-month period, several multiple times each after deterioration from APT use, and after Tesla-coil restoration the flat-test onset for vacuum electron emission determined. The resulting measured improvement of the vacuum breakdown voltage is displayed in Fig. 2, with an average improvement of (4.5±1.8) kV, and some LEs restored to a "like new" condition by an increase of the vacuum breakdown voltage by about 7-8 kV to above 11 kV. SEM imaging confirmed that no melting or damage to the LEs on a ...

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“…Accuracy in APT reconstruction is an important aspect but time consuming and not always easy to achieve [1]. Reconstruction based on lattice spacing is one of the more reliable methods to improve reconstruction accuracy [2][3]. Post-reconstruction analysis such as the 3D Hough transformation has been reported for pole indexing [4].…”

mentioning

confidence: 99%

Automated Crystallographic Identification of Atom Probe's Ion Desorption Map

et al. 2017

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Atom probe tomography can provide high accuracy analysis for local composition at the atomic-scale, but structural analysis often relies on alternative techniques that are carried out separately. However, atom probe results often already contain pieces of crystallographic information which can be used in identifying crystal structure, determining crystallographic orientation, and measuring lattice parameters of matrix and precipitate phases. It has similarities to conventional work using field ion microscopy, but rather than ionizing imaging gases, atom probe uses field evaporated ions for 3D chemical imaging.In crystalline materials, especially for metals, trajectory aberrations result in lower ion hit intensity at poles and zone lines, providing unique field desorption maps similar to crystal stereographic projection maps. Accuracy in APT reconstruction is an important aspect but time consuming and not always easy to achieve [1]. Reconstruction based on lattice spacing is one of the more reliable methods to improve reconstruction accuracy [2][3]. Post-reconstruction analysis such as the 3D Hough transformation has been reported for pole indexing [4]. In order to facilitate APT reconstructions using lattice spacing for known structure materials, we will demonstrate automated pole indexing using a customized OIM TM for IVAS TM software package from EDAX ® [5]. Here, the same algorithms used to index electron backscatter diffraction (EBSD) patterns are applied to atom probe field desorption maps.There are strong similarities between field desorption maps and EBSD patterns. Both show poles and zone lines of crystallographic projection maps. However, the mechanisms that create the patterns are different. EBSD patterns follow electron diffraction rules but field desorption maps are not bound by same these rules. For example, forbidden reflectors in electron diffraction can appear in the field desorption maps. A customized structure database is necessary to index field desorption maps accurately while relying on the same Hough transform.Patterns of well-ordered high purity materials are generally good and can be indexed automatically. Figure 1a and b show examples of high quality field desorption maps from BCC tungsten and FCC aluminum, respectively. In the output, the software provides several index solutions from which the user may choose. A confidence of indexing parameter and mismatch of fit are important parameters to examine in justifying the best choice for indexing. Figure 1c and d are maps after image processing superimposed with an index overlay. The best solution is the one with the highest index confidence and the lowest degree of mismatch.With the ability to index all the poles in a field desorption map, the reconstruction parameters can be adjusted to have optimized d-spacing values for all the poles. Figure 2a

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Atom Probe Microscopy and Materials Science

Cited by 46 publications

References 95 publications

Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

Improving Local Electrode Performance by Tesla Coil Electric Discharges

Automated Crystallographic Identification of Atom Probe's Ion Desorption Map

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