On-axis Transmission Kikuchi Diffraction in the SEM. Performances and Applications

Transcription

1 On-axis Transmission Kikuchi Diffraction in the SEM. Performances and Applications Etienne Brodu, Emmanuel Bouzy, Jean-Jacques Fundenberger Séminaire «les microscopies électroniques à Metz et à Nancy»

2 Plan of the presentation History of TKD TKD on-axis versus TKD off-axis Performances Future development Conclusion

3 History of TKD EBSD Conventional or off-axis TKD Bulk specimen Thin specimen Transmission EBSD from 10 nm domains in a scanning electron microscope R. R. Keller, R. H. Geiss, Journal of Microscopy 245, (2012) Decrease in interaction volume o o lateral spatial resolution: 5-10nm same hardware/software

4 History of TKD Conventional or off-axis TKD on axis-tkd Thin specimen Transmission Kikuchi Diffraction (TKD) via a horizontally positioned detector J. J. Fundenberger, E. Bouzy, D. Goran, J. Guyon, A. Morawiec, H. Yuan, Microsc. Microanal. 21, suppl. S3 (2015) very intense forward scattering Axis symmetrical configuration (similar to the TEM geometry)

5 History of TKD Orientation mapping by TEM from Kikuchi patterns (E.P.) TEM control Camera control Digital Micrograph Corrected patterns EP CM 200 Kikuchi / CBED Correction Line detection Indexation Orientation X Y «Polycrystal Orientation maps from TEM» J.-J. Fundenberger, A. Morawiec, E. Bouzy, J.-S. Lecomte Ultramicroscopy, Vol.96, (2003), 127.

6 History of TKD New TKD configuration called on-axis TKD Imagined, made and validated to LEM3 then marketed by Bruker Fundenberger J. J., Bouzy E., Goran D., Guyon J., Yuan H., Morawiec A. (2016) Orientation mapping by transmission-sem with an on-axis detector Ultramicroscopy, 161,

7 TKD on-axis versus TKD off-axis Low distortion Off-axis Pattern Center On-axis Pattern Center Induced by the gnomonic projection

8 TKD on-axis versus TKD off-axis Intense low-angle forward scattering On-axis TKD is fast 600 nm 1 h 48 min 130 ms Al-Mg by HPTT /20 6 min 7 ms paramount to avoid beam drift «On-Axis Versus off-axis TKD Technique: Application to the Characterization of Severe Plastic Deformation Induced Ultrafine Grained Microstructures» H. Yuan, E. Brodu, C. Chen, E. Bouzy, J-J. Fundenberger, L.S. Toth, Journal of Microscopy 267 (2017) 70-80

9 TKD on-axis versus TKD off-axis Intense low-angle forward scattering Low electron dose mode for light elements sensitive to electron irradiation damage a Spheroidal Graphite Quality pattern maps produced by on-axis TKD Typical diffraction pattern obtained with on-axis TKD IPF orientation maps over the quality pattern map

10 TKD on-axis versus TKD off-axis Large variety of diffraction contrasts Spot Kikuchi lines Kikuchi bands contrast inversion when sample thickness increases or electron energy decreases. Need of detection and indexation software dedicated to TKD Diffraction contrast dependence on sample thickness and incident energy in on-axis Transmission Kikuchi Diffraction in SEM E.Brodu, E.Bouzy, J.-J. Fundenberger Ultramicroscopy 181 (2017) 123.

11 Performances Angular resolution Depends on: 1- the patterns 2- the software ESPRIT 2.0 by BRUKER Cross-correlation with ATOM (Beausir & Fundenberger, LEM3)

12 Performances Lateral spatial resolution On-axis TKD orientation mapping of nanocrystalline materials in SEM E. Brodu, E. Bouzy, J.-J. Fundenberger, J. Guyon, A. Guitton, Y. Zhang Materials Characterization 130 (2017) 92.

13 Performances Lateral spatial resolution Physical lateral resolution = 6-9 nm Effective lateral resolution = 3-6 nm How to improve the lateral resolution? -> decrease the beam broadening through the sample : thin samples (<100 nm) and high energy (30 kev)

14 Performances Depth resolution E 0 Z e 20nm 60nm below the exit (bottom) face of the specimen (according to the electron energy E 0 and the atomic number Z of the material).

15 Performances Depth resolution

16 Performances Depth resolution Generation of Kikuchi patterns in each layer because of internal divergent electron sources + Absorption along the travel to the bottom of the specimen function of depth = The last layers are the most visible fin Linear dependence of the depth resolution with the electron energy épais E. Brodu, E. Bouzy «Depth resolution dependence on sample thickness and incident energy in on-axis Transmission Kikuchi Diffraction, submitted to Microscopy and Microanalysis

17 Performance of the different methods EBSD TEM Kikuchi TEM spots TKD Geometry reflection transmission transmission transmission Angular resolution 1 > Lateral spatial resolution nm < 10nm (LaB 6 ) 2 5nm (FEG) < 10nm (LaB 6 ) 2 5nm (FEG) 3-5nm Depth resolution Sample Sample ~ 10nm 20 60nm thickness thickness

18 Future developments PhD Thesis of Clément Ernould with Vincent Taupin, Benoit Beausir, Jean-Jacques Fundenberger, Etienne Brodu, Emmanuel Bouzy Complete geometric characterization of interfaces Orientation gradients Geometrically Necessary Dislocations Density Elastic strain map

19 On-axis TKD for orientation mapping in SEM Summary - Intense low-angle forward scattering: On-axis is much faster than conventional TKD ( 20) Low dose mode for specimens sensitive to electron irradiation damage - Angular resolution should be at least as good as HR-EBSD. - Lateral spatial resolution of the order of 3-6 nm. - Depth resolution of the order of nm for Si with a linear dependence on energy. - Suitable for nanomaterials investigations due to both good lateral and depth resolutions.

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