A Diffraction Simulation and Comparison C.T. Koch, J. Mller, S. - - PowerPoint PPT Presentation

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$a diffraction simulation and comparison$

Mar 26, 2023 186 likes •351 views

A Diffraction Simulation and Comparison C.T. Koch, J. Mller, S. Fairman, B. Haas Humboldt University of Berlin Plugin for Nionswift Department of Physics Page 3 C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors

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A Diffraction Simulation and Comparison Plugin for Nionswift

C.T. Koch, J. Müller, S. Fairman, B. Haas Humboldt University of Berlin Department of Physics

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 3

Research within the Structure Research / EM group

δ δ

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 7

Large-Angle Rocking-Beam Electron Diffraction

Individual pattern LARBED pattern (log scale) Sample: SrTiO3, not energy filtered, microscope: Zeis EM912, 120 kV

LARBED data acquisition by QED Plugin to DigitalMicrograph (HREM Research)

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 8

From PED => LARBED

LARBED preserves the rocking curve information ! Sample: Si (110) zero-loss-filtered

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 9

Extracting LARBED Discs from data stacks

9

= 8°

Each pixel within the discs is the integrated background-subtracted Bragg intensity

SrTiO3 (001)

not energy-filtered

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 10

Correcting Ewald-Sphere Curvature & Separating Laue Zones

Sum of all frames Extracted Zero-Order Laue Zone 3D View

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 11

Ab-initio Structure Factors Fitting to SrTiO3 LARBED data

unit cell

Experiment ab-initio Fit Difference

IAM potential (121 beams) Fit to exp. (121 beams) Fit to exp. (incl. unmeas. data 456 beams)

F. Wang, et al. Phys. Rev. Lett. 117 (2016) 015501

Feng Wang

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 12

LARBED on a 60 nm MgO cube

C.T. Koch et al. Microsc. Anal. (2012)

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 13

3D Reconstruction of k-Space for Complex Structure

Reconstructed 3D k-space Volume from experimental LARBED data

z-axis expanded x 5

Sample: K2O∙7Nb5O2 (a=b=2.9 nm, c = 0.39 nm) Rocking curves for each spot in 3D k-space

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 14

LARBED at low kV and variable camera length

MoS2 @ 30 kV tilt = 0° to 9° in 1° Graphene oxide @ 30kV L = 36.5 – 8.5mm MoS2 @ 30kV L = 36.5 – 11.5mm 3D reconstruction from LARBED on graphene @ 30 kV

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 15

Nion Swift GUI => Manual Control & Python Scripting

 Scripts will work both on the SEM and (hopefully soon) on Nion scope

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 16

4D-STEM in the SEM

4D-STEM of graphene

xide @ 30kV

Layer counting in WS2 Grain orientation in graphene Two flexible scanning options:

Beam positioning commands to

SEM API (slow)

External scan generator (fast)

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 17

A Diffraction Simulation Plugin

Uses modules pymatgen and vtk

(both installed using pip install)

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 18

DIADEM-Server Data archiving and evaluation software Data Metadata Data Metadata + in-band Metadata Data base for Metadata Data acquisition at microscope Data processing by user new Metadata + new in-band Metadata 100GbE GPU-Servers

Managing Large Data & Data Science

Decentralized Independent Archives of Data for Electron Microscopy (DIADEM)

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 19

Fast Bloch-wave simulations with GPUs - Update 66.19x 90.06x 63.08x 97.25x

10 20 30 40 50 60 70 80 90 100 500 1000 1500 2000 2500 3000 3500 4000 Speedup multiplier

vs. conventional method

Number of reflections MAGMA cusolver

Combination of a matrix-exponential approximant & GPU hardware = quick forward simulations without sacrificing numerical accuracy [1]

[1] R. S. Pennington, F. Wang, and C. T. Koch, Ultramicroscopy 141, 32 (2014).

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C.T. Koch | Humboldt University of Berlin | STEM with Advanced Detectors 4.-7.9.2018 Page 20

Summary

In 4DSTEM, it makes sense to vary 𝑙𝑗𝑜,⊥ and also 𝑠

=> possibility for solving local structure => local 3 reciprocal space lattice => shape transform of nanocrystals => effect of aberrations can be compensated

4DSTEM in the SEM ideal for mapping local
orientation & phase
strain and E-field
ideal for 2D materials
6-axis goniometer + variable camera length

transmission diffraction setup => very flexible => many aplications => mapping of beam-sensitive materials

Being able to simulate electron diffraction within