The University of Alabama 1 st APT Workshop for Earth Sciences

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1 The University of Alabama 1 st APT Workshop for Earth Sciences January 2016 David Reinhard LEAP

Microstructure characterization technique (UHV) that uses field evaporation (high

Position sensitive detection (PSD) system yields lateral spatial information (x,y) and

yields chemical information (m/n) Near-atomic resolution in all three dimensions High

) Specimen (cooled) Position sensitive detector z x y Field evaporated ions (laser pulse)

2 Microstructure characterization technique (UHV) that uses field evaporation (high electric field) to remove atoms from a needle-shaped substrate (apex radius ~ nm) Position sensitive detection (PSD) system yields lateral spatial information (x,y) and order of atom evaporation yields depth spatial information (z) Time-of-flight technique yields chemical information (m/n) Near-atomic resolution in all three dimensions High voltage (d.c.) Specimen (cooled) Position sensitive detector z x y Field evaporated ions (laser pulse) Start time (t 1 ) Stop time (t 2 ) Atom Probe Tomography Flight time signal Data = (x,y,z,mass) Pt Co ~10 nm Time-of-Flight converted to Mass-to-Charge m/n (t 2 -t 1 ) 2 4 May

3 Field Evaporation: Model & Experiment Field Evaporation Simulation Field Evaporation of BCC Metal O Dimond (University of Oxford) B. Gault (Universite de Rouen) 4 May

Reconstruction: How to Calculate x, y, and z Specimen Radius Magnification Depth F = Voltage / (k*r) or R = V/Fk Knowledge of the specimen radius throughout the acquisition is required V is the

4 Reconstruction: How to Calculate x, y, and z Specimen Radius Magnification Depth F = Voltage / (k*r) or R = V/Fk Knowledge of the specimen radius throughout the acquisition is required V is the specimen voltage F is the material evaporation field (constant) k is the field reduction factor (constant) M d R Magnification is the key calculation for the xy transformation from detector space to specimen space d is distance between specimen and detector is the image compression R is the average radius of the specimen z z 2 M A A z increment must be calculated in order to transform from ion arrival number to z in specimen space is the atomic volume A is the detector area is the efficiency 4 May

Strengths of the Reconstruction Model Z positions are

Further, the precision of the Z resolution can be

5 Strengths of the Reconstruction Model Z positions are constructed from projection of X,Y measurements into a simple, geometric model. But for many specimens it works very well. Further, the precision of the Z resolution can be substantially better than the lateral resolution in crystalline metals that evaporate well (pure tungsten example shown below) 4 May

Magnification (XY Projection) M Limitations of the Primary Assumptions d

, Journal of Microscopy 241(3) (2011) 225 The assumed reconstruction

errors between the assumed radius (shape) and the actual field

evaporated specimen shapes often deviate substantially from

electron microscopy and simulation B. Loberg and H.

6 Magnification (XY Projection) M Limitations of the Primary Assumptions d R Depth (Z Increment) z 2 M A Assumption Reality Experiment E. A. Marquis et al., Journal of Microscopy 241(3) (2011) 225 The assumed reconstruction radius is contained in both equations: Magnification & Depth Thus any errors between the assumed radius (shape) and the actual field evaporated shape affect all dimensions in the reconstruction Field evaporated specimen shapes often deviate substantially from hemispherical This conclusion is based on observations from both electron microscopy and simulation B. Loberg and H. Norden, Arkiv for Fysik 39 (1968) 383 T. Wilkes et al., Metallography 7 (1974) 403 Image courtesy J. Lee (Samsung) 4 May

7 IVAS Radius Evolution Options IVAS currently supports two geometric models and one user-defined model: 1) Voltage Recon 1) Tip Radius directly tied to total voltage by a user specified (KF) conversion factor 2) Shank angle is assumed to be 0 for volume increment corrections. 2) Constant Shank Recon 1) Initial radius is fixed by initial voltage 2) Radius evolves based on specified shank angle and accumulated atomic volume 3) Tip Profile Recon 1) (Pre-analysis) Image based Tip Radius evolution 2) Manual ability to force any radius profile you want to try Voltage Evolution R T R V T 0 V0 RT R 0 wz T Constant Shank Angle Evolution Tip Profile Evolution 4 May

reconstructed with each of the three radius evolution methodologies Regardless of the method selected, the

8 Voltage Evolution Example of Radius Evolution Options Constant Shank Angle Evolution Tip Profile Evolution Cr Ni Cr Ni Cr 39nm 30nm 46nm 34nm 51nm 46nm 55nm 63nm 55nm 53nm 52nm 54nm 62nm 54nm 59nm A NiCr multilayer sample reconstructed with each of the three radius evolution methodologies Regardless of the method selected, the height and width of the recon will still be subject to the selection of other reconstruction parameters 4 May

9 Influence of ICF and Radius Variations for a Fixed Shank Angle (15º) 119.5nm 82nm 60nm 106.5nm 65.5nm ICF1, R75 ICF1.5, R75 ICF2, R75 ICF1, R100 ICF1.5, R100 89nm 51.5nm 32nm 43.5nm ICF2, R100 ICF1, R125 ICF1.5, R125 ICF2, R125 4 May

Double lines Single line Tungsten Single Crystal: An

with d-spacing Correct indexing 114 114 103 001 001

both of them are good fit The one on the left is

10 Double lines Single line Tungsten Single Crystal: An Example of Verifying Correct Reco. with d-spacing Correct indexing Incorrect indexing 103 Two ways of pole indexing and both of them are good fit The one on the left is correct indexing Double zone lines from (114) pointing the (001) pole 4 May

11 Correct d-spacing on Major Poles Plane spacing on the major poles nm for (001) nm for (013) nm for (114) The reconstruction explorer feature in IVAS can allow for efficient exploration of the available parameter space for a reconstruction The spatial distribution map (SDM) can then be used to measure the plane spacing for a specific pole to evaluate the quality of the reconstruction 4 May

12 Confirm Lattice Along Major Poles (-1-14) (-1-16) (001) (116) (114) X-Y SDM map X-Y SDM map 2 nm In the best cases the latest planes will be visible at multiple poles (they will be most clear when the planes are perpendicular to the analysis direction 4 May

Before After Reconstruction Optimization through SEM Imaging Default

zircon specimen Specimen was imaged before and after acquisition The default

from the SEM The evaporation physics of zircon are not well understood so the

improved by using the information from the SEM images and the nature of the

13 Before After Reconstruction Optimization through SEM Imaging Default Reconstruction After run tip radius R=107 nm 711 nm (cs) Reconstruction of a zircon specimen Specimen was imaged before and after acquisition The default reconstruction does not show good agreement with the estimated analysis depth from the SEM The evaporation physics of zircon are not well understood so the correct parameters are not known The accuracy of the reconstruction can be improved by using the information from the SEM images and the nature of the sample Variable parameters Shank angle Atomic density ICF Evaporation field K factor Efficiency 4 May

progression of defined radii Atomic density set to the known density of

023 nm 3 /atom) ICF used default value Evaporation field set by the

14 Tip Profile Reconstruction Tip profile reconstruction Optimized Reconstruction Variable parameters Shank angle prescribed by the progression of defined radii Atomic density set to the known density of zircon (0.023 nm 3 /atom) ICF used default value Evaporation field set by the defined radii through the R = V/KF relationship K factor set by the defined radii through the R = V/KF relationship Efficiency used default value 4 May

15 Analyses

16 Atom Probe Tomography Data Format Atom Map Cr Co Cu Selected Area Atom Map 80x80x60nm 35x35x14nm Mass Spectrum 4 May

17 APT of Thin Films: Spectra Analysis Cr Co Cu Cu Selected area mass analysis provides very fast evaluation of what is present in what regions of space 4 May

18 APT of Thin Films: Interfacial Chemistry Cr Co Cu 10-90% width Composition plotted vs. distance provides estimates of interfacial chemistry 4 May

APT of Thin Films: Interfacial Morphology Cr

%Co isoconcentration surface RMS roughness 0.

investigated using by visualizing interfaces

concentration (iso-concentration surfaces)

calculated using this construct* ISO 4287/1:

19 APT of Thin Films: Interfacial Morphology Cr Co Cu 50at.%Co isoconcentration surface RMS roughness 0.37nm Interfacial morphology chemical can be investigated using by visualizing interfaces that divide regions of specified concentration (iso-concentration surfaces) Interfacial roughness estimates may be calculated using this construct* ISO 4287/1: RMS roughness 0.67nm * R. W. O Neill et al., Microscopy and Microanalysis 2006, 12(S2), 1746CD 4 May

20 Concentration (at.%) Carbon Concentration (at.%) APT of Thin Films: Interfacial Analysis by Proxigram* Cr Co Cu C Distance (nm) C ++ C + Cr Co Cu The proximity histogram (or proxigram ) creates a concentration profile by summing all atoms in bins that are a constant Middle distance of away Co from layer an isoconcentration surface Statistics are improved in this method, and effects of curvature may be removed but the overall nature is averaged by using a proxigram * O. Hellman et al., Microscopy and Microanalysis 2000, 6, May

21 TOF Mass Spectrum (Ni-based superalloy) Light elements Al 2+ SCIENCE & METROLOGY Mo 2+ SOLUTIONS Cr 2+ Fe Co2+ 2+ Ni 2+ Nb 2+ Ta 3+ W3+ W 2+ Al 3+ Ti 3+ B 2+ B + Si 2+ C 2+ C + Ti 2+ Ta 4+ Mo 3+ 4 May 2015 (100x100x250 nm) 21

64 Ni & 96 Mo Peak Decomposition of Overlaps Peak decomposition attempts to correct for direct peak overlaps Ni 2+ Isotope m/n Abundance 58 28.9675 68.077 60 29.9655 26.223 61 30.4655 1.139 62 30.

22 64 Ni & 96 Mo Peak Decomposition of Overlaps Peak decomposition attempts to correct for direct peak overlaps Ni 2+ Isotope m/n Abundance Total: 100 Mo 3+ Isotope m/n Abundance Total: Case of ( 64 Ni 2+, 96 Mo 3+ ): Compare isotopic abundances of Ni and Mo on the mass spectra with natural abundances: ratios comparison by pairs. Mathematical solving of linear equations to satisfy the conditions for both elements. Copyright, CAMECA Instruments Inc May

23 Compositional Imaging Al-Ti-Cr rich phase 20 nm slice Ta Al Co-Cr rich phase Ti Visualization of local composition Cr Fe Co Mo 4 May

Particle Element No ions At % Ni 11929 62.

63% Cr 679 3.58% ~ 4 nm Mo 541 2.85% W 246 1.

24 Local Compositional Analysis Interface Visualization Precipitate atoms Composition of Particle Element No ions At % Ni % Al % Co % Ti % Cr % ~ 4 nm Mo % W % Ta % B % Fe % Nb % Si % Selected Volume Mass Spectrum Ti Cr Ni, Co, Mo Mo, Nb W, Ta Selected volume analysis 4 May

25 Traditional 1-D profile Compositional Profiling: 1-D and Proxigram Profile SCIENCE & METROLOGY Local CompositionSOLUTIONS Proximity Histogram Interface (Proxigram*) Method ~ 4 nm Matrix ( ) Precipitate ( phase) *O. C. Hellman, J. A. Vandenbroucke, J. Rusing, D. Isheim, and D. N. Seidman, Microsc. Microanal. 6, May

Digging for Gold at the Atomic Scale Carbon-coated quartz sample Pre-characterized using EPMA Arsenopyrite (FeAsS) and Loellingite (FeAs2) are the primary constituents Arsenopyrite grains contain

26 Digging for Gold at the Atomic Scale Carbon-coated quartz sample Pre-characterized using EPMA Arsenopyrite (FeAsS) and Loellingite (FeAs2) are the primary constituents Arsenopyrite grains contain ~100ppm of elemental Au Au Mα The objectives were Determine the spatial distribution of Au Demonstrate the feasibility of using APT analysis to understand local Au compositions Au region not visible in FIB/SEM 4 May

27 Gold distribution Control Location No Au detected Detection limit from control determined to be ~ 5ppm Au detected Peak ~ 1200 ppm Au detected 4 May

28 Sb observed in all data sets In the gold-free data set the Sb concentration was ~34ppm In the three data sets with gold the Sb concentration ranged from ~11-14ppm Cu was tentatively identified in the three data sets with gold The Cu concentration in the three data sets ranged from ~25-45ppm Sulfur also detected as molecular species Sb Trace Elements Cu S 2 S 2 As 2 S Sb Cu Au S 2 AuH 2 Sb Cu 4 May

learn about the evaporation characteristics of a new material, the

29 Zircon Standard BR266 New applications can often benefit from investigation of well-characterized standards This can help us to learn about the evaporation characteristics of a new material, the range of acceptable acquisition parameters, the typical data quality, etc. 4 May

30 Si O SiO Zr Si Zr Zircon standard mass spectrum Zr, Si, O, and combinations of those species make up the majority of the peaks All uncertainties calculated in this work are ± 2 O 2 ZrO SiO ZrSiO 3 ZrO SiO 3 HfO Si 2 O 3 Zr ZrO Zircon Standard SiO 2 Bulk concentrations in the analyzed volume: U: 141 ± 6.6 ppm Pb: 12 ± 2.5 ppm Th: 32 ± 3.1 ppm Hf: 1447 ± 14.2 ppm Nominal published bulk concentrations: ZrO 2 U: 909 ppm Pb: 79.8 ppm Th: 201 ppm Hf: 8220 ppm The 206 Pb to 238 U ratio in the analyzed volume is ± Si 2 O 3 & 208 Pb overlap Si 2 O 4 U ThO 2 Pb UO UO Pb R52_ May

31 Ion Maps of BR266 Si Zr O U Pb R52_ Selected ions maps shown above Ion distribution appears to be homogenous except for 2 small Pb clusters 4 May

Single-Cluster Analysis When restricted to just the clustered volume

experiment, 1 contained another cluster The The 207 Pb/ 206 Pb

049 These results in good agreement with the published TIMS ratio of

combination of additional data When the data from the two clusters

32 Single-Cluster Analysis When restricted to just the clustered volume a very small 207 Pb peak can be observed The 207 Pb/ 206 Pb ratio: ± Additional data sets were acquired after an annealing experiment, 1 contained another cluster The The 207 Pb/ 206 Pb ratio: ± These results in good agreement with the published TIMS ratio of The uncertainty can be reduced through analysis and combination of additional data When the data from the two clusters are SCIENCE & METROLOGY combined the ratio SOLUTIONS is ± ºC anneal 206 Pb 0.2 Pb ions per nm 3 iso-density surface 207 Pb Si 2 O 3 & 208 Pb overlap R52_ R52_ R52_ May

33 808 nm Y-rich clusters in a 4.4 billion year old zircon Localized Pb Ratio Dating Pb signal from the full data set Si 2 O 3 + Pb 208 Pb signal from inside the Y-rich features Pb 206 Pb 207 Si 2 O 3 + Pb 208 Pb signal from outside the Y-rich features Si 2 O 3 + Pb 208 Pb 206 Pb 207 Pb 206 In geological zircon samples the ratio of radiogenic Pb is often used to measure the age of the sample In the example shown here, Y and Pb-rich clusters are observed Measuring and comparing the Pb ratios in the full data set, the matrix, and the clusters can provide useful information about the age of the sample and the dates of important heating events However the low concentration of Pb makes this measurement challenging outside of the clusters The measurement can be improved by combining data from multiple data sets Valley et al. Nature Geoscience (2014). 4 May

34 Combining Data to Improve Statistical Confidence Pb signal from outside the Y-rich features Single data set Si 2 O 3 + Pb 208 Pb signal from outside the Y-rich features Two data sets Si 2 O 3 + Pb 208 Pb 206 Pb 207 Pb 206 Pb Pb / 206 Pb ratio: 0.31 ± (2 sigma) 207 Pb / 206 Pb ratio: 0.30 ± (2 sigma) By combining multiple data sets the signal-to-noise in the mass spectrum can be improved With sufficient time and specimens higher sensitivity can be achieved 4 May

35 Thank you for your attention. Questions? 4 May

SUPPLEMENTARY INFORMATION

SUPPLEMENTARY INFORMATION DOI: 10.1038/NGEO2075 Appendixes: Hadean age for a post-magma-ocean zircon confirmed by atom-probe tomography JOHN W. VALLEY, AARON J. CAVOSIE, TAKAYUKI USHIKUBO, DAVID A. REINHARD,