From Imaging Conductivity to Imaging Electron Density

Invited talk given at Microscopy and Microanalysis conference in 2024. Describes progress in the development of the Secondary Electron EBIC (SEEBIC) technique. In particular, shows SEEBIC applied to single atoms where direct imaging of atomic electron density is revealed.

1. From imaging conductivity to imaging electron density Ondrej Dyck Jawaher Almutlaq David Lingerfelt Jacob Swett Charalambos Evangeli Andrew Lupini Jan Mol Dirk Englund Stephen Jesse

2. Tunneling-based DNA sequencing Puczkarski, P.; Swett, J. L.; Mol, J. A. Graphene Nanoelectrodes for Biomolecular Sensing. J. Mater. Res. 2017, 32 (15). Electroburning Au electrode Au electrode Graphene Au electrode Au electrode Graphene Nano-gap DNA Sequencing Jacob Swett Arizona State University

3. Sarwat, S. G.; Gehring, P.; Rodriguez Hernandez, G.; Warner, J. H.; Briggs, G. A. D.; Mol, J. A.; Bhaskaran, H. Scaling Limits of Graphene Nanoelectrodes. Nano Lett. 2017, 17 (6), 3688–3693. https://doi.org/10.1021/acs.nanolett.7b00909. Conductance switching Quantum dot formation P. Fried, J.; Bian, X.; L. Swett, J.; I. Kravchenko, I.; D. Briggs, G. A.; A. Mol, J. Large Amplitude Charge Noise and Random Telegraph Fluctuations in Room-Temperature Graphene Single-Electron Transistors. Nanoscale 2020, 12 (2), 871–876. https://doi.org/10.1039/C9NR08574B. Prins, F.; Barreiro, A.; Ruitenberg, J. W.; Seldenthuis, J. S.; Aliaga-Alcalde, N.; Vandersypen, L. M. K.; van der Zant, H. S. J. Room-Temperature Gating of Molecular Junctions Using Few-Layer Graphene Nanogap Electrodes. Nano Lett. 2011, 11 (11), 4607–4611. https://doi.org/10.1021/nl202065x. Anthracene-functionalized curcuminoid molecules (1,7-(di-9-anthracene)-1,6-heptadiene-3,5-dione, abbreviated as 9Accm Within the Nano-Gaps

4. Low noise High temperature compatible Cryo compatible In-situ electrical contacting Interchangeable configurations Wafer-scale STEM compatible Sample Platform

5. Prototype devices can be operated in situ HAADF Current-voltage trace Electrode SiN window Graphene 500 nm Electrode

6. Prototype devices can be operated in situ 500 nm Electrode Electrode SiN window Aperture Graphene

7. We can hardly see anything UCLA Matthew Mecklenburg William (Billy) Hubbard Chris Regan Develop a new imaging mode! (From scratch?)

8. Dyck, O., Swett, J.L., Lupini, A.R., Mol, J.A. and Jesse, S. (2021), Inside Front Cover: Imaging Secondary Electron Emission from a Single Atomic Layer (Small Methods 4/2021). Small Methods, 5: 2170013. https://doi.org/10.1002/smtd.202170013 SEEBIC Imaging

9. SEEBIC Mask Vacuum Single Double Triple Quadruple SiN Other 100 nm SEEBIC Intensity Histogram Mean Relative Intensity HAADF Against All Odds At least 11 electrical connections from the sample to the TIA Graphene is notorious for its low secondary electron yield (used as a coating to suppress secondary electron emission) Nano Electronic Imaging

10. SEEBIC 100nm HAADF Contamination Boosts Emission

11. Seeing the Invisible

12. SEEBIC on Operational Devices 500 nm HAADF SEEBIC (raw) SEEBIC (smoothed)

13. Connectivity Diagnostics

14. Sample Platform

15. a) common band diagram of a Metal-Insulator-Metal (MIM) stack demonstrating PF emission, b) detailed band diagram, demonstrating PF emission, where qΦ is the ionization potential and β√E is the amount by which the trap barrier height is lowered by the applied electric field (E) and β is the PF field lowering coefficient.

16. Electroburning Au electrode Au electrode Graphene Au electrode Au electrode Graphene Nano-gap Forming Nano-gaps In Situ

17. Source Drain Forming Nano-gaps In Situ

18. Formation of New Conductive Pathways

19. HAADF HAADF SEEBIC Non-Ohmic Nano-gap

20. SEEBIC Detection of Conductance Switching

21. Clustering Closer Look at the Observed Intensities

22. Closer Look at the Observed Intensities

23. TIA TIA TIA Real signal Quantum dot, filamentation, molecular bridging Charging/discharging through the non-ohmic region An initial step in correlating device operation with high resolution imaging and conduction mapping Main Conclusions

24. This is a bulk description Real materials are composed of individual atoms Can we see them? Down to a Single Atom We tried on graphene but: Contamination Low SE yield

25. Getting More Electrons with Heavier Atoms MIT Jawaher Almutlaq

26. Sample Overview with SEEBIC

27. Single Atom Resolution? Clear Atomic Information Very Murky!!! SEEBIC 100 nm HAADF Mask Previous Strategy

28. Finding Atoms Intensity Histogram W Se-Se

29. Classifying Atoms Tiling to get local information ‘Ravel’ the tiles into feature vectors K-Means Clustering

30. Information Transfer (Black Magic)

31. Resolving Single Atoms with SEEBIC