Comparative Apex Electrostatics of Atom Probe Tomography Specimens

Zhang, Qihua; Klein, Benjamin; Sanford, Norman A.; Chiaramonti, Ann N.

doi:10.1007/s11664-021-08932-6

Cited by 6 publications

(5 citation statements)

References 26 publications

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“…Background for this approximation is presented elsewhere. [24] Given the apex diameter and bias voltage for the tip under discussion (recon 32), we find that k = 4.0, i.e., well within the span of validity. However, it must be kept in mind that the specimen tip is an n-type semiconductor, and although it is biased to depletion under the SV, a p-type inversion layer forms on a region of the tip encompassing the apex.…”

Section: Isotropic Approximationmentioning

confidence: 54%

“…A more detailed exposition of our electrostatic analysis, and comparison with the k-factor approximation, is given elsewhere. [24] A schematic of the tip-electrode geometry is given in Fig. 20.…”

Section: Electrostatic Analysis Of Gan Specimen Tipsmentioning

confidence: 99%

“…A brief summary of the electrostatic analysis is presented in Section 4 with a more extensive development presented in Ref. [24]. A discussion of experimental and analytical uncertainties is included in Section 5 and conclusions are presented in Section 6.…”

Section: Introductionmentioning

confidence: 99%

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Laser-assisted atom probe tomography of c-plane and m-plane InGaN test structures

Sanford¹,

Blanchard²,

Brubaker³

et al. 2022

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Laser-assisted atom probe tomography (L-APT) was used to measure the indium mole fraction x of c-plane, MOCVD-grown, GaN/InxGa1-xN/GaN test structures and the results were compared with Rutherford backscattering analysis (RBS). Four separate sample types were examined with x = 0.030, 0.034, 0.056, and 0.11 as determined by RBS. The respective InxGa1-xN layer thicknesses were 330 nm, 327 nm, 360 nm, and 55 nm. L-APT data were collected under (fixed) laser pulse energy (PE)conditions in the range of (2 1000) fJ. Sample temperatures were generally 54 K. The data were analyzed using different region-of-interest (ROI) volumes to establish criteria for both data collection and compositional analysis that would return L-APT results that fell within the estimated 0.5 at. % uncertainty of RBS. Using cylindrical ROIs placed coaxially within the reconstructed InxGa1-xN regions, and with ROI depths of (55 180) nm, PE values in the range of(2 100) fJ yielded indium concentrations that conformed to RBS. L-APT results were comparatively insensitive to ROI diameter such that 20-nm-diameter coaxial ROIs yielded indium concentrations nearly equal to ROIs that encompassed the full InxGa1-xN regions. By contrast, for the GaN portions of the samples, L-APT would only yield near-stochiometric composition for PE in the range of (5 20) fJ with the analysis restricted to coaxial ROIs of diameters ?20 nm. m-plane oriented L-APT specimens were derived from core-shell GaN/InxGa1-xN multi-quantum-well structures. Analysis within ROIs placed along [0001] of these m-plane samples revealed a spatial asymmetry in charge-state ratios that is consistent with an electrostatic effect arising from spontaneous polarization. Both c-plane and m-plane sample types showed depth-dependent variations in absolute ion counts that depended upon ROI placement.

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Section: Isotropic Approximationmentioning

confidence: 54%

Section: Electrostatic Analysis Of Gan Specimen Tipsmentioning

confidence: 99%

See 1 more Smart Citation

Laser-assisted atom probe tomography of c-plane and m-plane InGaN test structures

Sanford¹,

Blanchard²,

Brubaker³

et al. 2022

View full text Add to dashboard Cite

show abstract

“…Considering the tip apex diameters before and after APT analysis, and the span of the standing voltage over the course of the data acquisition runs, we estimate the surface electric field enabling field evaporation from these specimen tips is in the approximate range of 20-50 V/nm. Details on estimating the surface electric field at an APT tip apex may be found in Zhang et al (2021); Larson et al (2013).…”

Section: Titanium-aluminum Alloymentioning

confidence: 99%

“…The specimen must be sufficiently robust to avoid fracture during data acquisition and the key to suc-cess is to minimize the integrated stress, yet still apply an electric field strong enough to facilitate field evaporation. However, the issue of electrostatic stress in the vicinity of the specimen apex can be quite complex, spatially discontinuous, and depend upon the dielectric, metallic, and semiconducting properties of the constituent layers that may be present (Zhang et al, 2021). In practice, tip diameters of <100 nm are typically necessary in order to produce a sufficiently high electric field locally at the tip apex.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Specimens for Atom Probe Tomography using a Combined Gallium and Neon Focused Ion Beam Milling Approach

Allen¹,

Blanchard²,

Lake³

et al. 2023

Preprint

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We demonstrate a new focused ion beam sample preparation method for atom probe tomography. The key aspect of the new method is that we use a neon ion beam for the final tip shaping after conventional annulus milling using gallium ions. This dual-ion approach combines the benefits of the faster milling capability of the higher current gallium ion beam with the chemically inert and higher precision milling capability of the noble gas neon ion beam. Using a titanium-aluminum alloy and a layered aluminum/aluminum oxide material as test cases, we show that atom probe tips prepared using the combined gallium and neon ion approach are free from the gallium contamination that typically frustrates composition analysis of these materials due to implantation, diffusion, and embrittlement effects. We propose that by using a focused ion beam from a noble gas species, such as the neon ions demonstrated here, atom probe tomography can be more reliably performed on a larger range of materials than is currently possible using conventional techniques.

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Learning Atom Probe Tomography time-of-flight peaks for mass-to-charge ratio spectrometry

Coakley

Sanford

2022

Ultramicroscopy

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Comparative Apex Electrostatics of Atom Probe Tomography Specimens

Cited by 6 publications

References 26 publications

Laser-assisted atom probe tomography of c-plane and m-plane InGaN test structures

Laser-assisted atom probe tomography of c-plane and m-plane InGaN test structures

Fabrication of Specimens for Atom Probe Tomography using a Combined Gallium and Neon Focused Ion Beam Milling Approach

Learning Atom Probe Tomography time-of-flight peaks for mass-to-charge ratio spectrometry

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