Scanning probe microscopy upwards into 3D

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(wiki-TODO: Add figures from the paper.)

Experimentally demonstrated

With stiff cantilever AFM using the CO probing method:

  • First using STM (current through the picked up CO) slightly off-site to reproducibly get a reference height
  • Then going up and in nc-AFM constant height mode, and scanning the very high up top flat area of
    small polyadamantanes (nanodiamonds). Note that this is higher up than the length of the probing CO molecule!
  • There at the top well resolving the diamond (111) face hydrogen termination structure.
  • Avoiding to accidentally shift around the extremely weakly to gold bond polyadamantanes
  • Avoiding to accidentally pick them up onto the SPM-needle-tip apex
  • Avoiding to accidentally toppling over the vertical standing ones (less likely since its more like sticking than lying due to vdW forces vastly exceeding gravity).
  • Scanning of hydrogen atoms that were hidden due to lying slightly lower by ramping down the scanning height

Why may this be relevant and promising?

Why is this a significant advance pointing to the eventual feasibility of
force applying mechanosynthesis of 3D structures like crystolecules?

Scanning 3D structures so far has been an Achilles heel of scanning probe microscopy (both STM and stiff cantilever AFM).
(wiki-TODO: Link the paper of nc-AFM scanned DNA, showing that images of slightly higher structures without flat top typically become distorted or at least non-interpretable.)

Here it has been shown that one can "jump up" a huge deal and scan up there with no losses in resolution and interpretability.
And without crashing the SPM-needle-tip-apex (big and blunt at this scale) into the high molecules on the surface

As is what the (for this reason not used) constant feedback (~ stiffness) scanning mode would do.
Scratching whit the "blunt" SPM-needle-tips side up the sharp edge of the atomically precise product.
See: SPM user interfaces

Notes

Yes, This experiment was merely very gentle scanning. No strong bonding interactions.
But with structures stronger anchored to the supporting surface
much stronger interactions should be possible too.
Potentially enabling force applying mechanosyntehsis being performed up there up top.

The ramping must have been a significant effort judging from the papers mention of (being glad to) not needing to do it again due to the associated slight slant.
There may be a lot to be gained by improvement on SPM control software for automating such such rampings and related operations.
Related: SPM user interfaces

The flat top of these polyadamnatanes was really critical here to get well interpretable images (without computational simulations even).
Force applying mechanosyntehsis may operate much like a 3D-printer, adding material layer-by-layers, so one always has quite flat top to work with.
High molecules with nigh perfectly flat top are quite rare thus there are not many experimental examples.
Nanotubes are one case. (TODO: Link relevant nanotube paper & eventually find more examples.)

Related pages

External links

★ [Ebling2018] Ebeling, Daniel & Šekutor, Marina & Stiefermann, Marvin & Tschakert, Jalmar & Dahl, Jeremy & Carlson, Robert & Schirmeisen, André & Schreiner, Peter. (2018). Assigning the absolute configuration of single aliphatic molecules by visual inspection. Nature Communications. 9. 10.1038/s41467-018-04843-z.
https://www.nature.com/articles/s41467-018-04843-z

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