Why gemstone metamaterial technology should work in brief

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(wiki-TODO: Page lost it's claimed brevity, needs split-up eventually.)

The idea of atomically precise gemstone based on-chip factories and their technology has faced major disbelieve and push-back in the past.
Here are the probably hardest arguments for this tech to be actually possible summarized in as brief a way as possible.

Regarding concerns about friction

Coaxial nanotube bearing based nano-motors have been experimentally built and tested. While still very crude they already show very little friction. Much unlike the problems with sticktion and wear in photolithographically produced MEMS systems. – Coaxial nanotubes are quite similar in characteristics to crystolecule bearing so the working nanotube bearings give experimental evidence for crystolecular elements working with low friction an wear free.

Concerns about friction have been experimentally dispelled (not only theoretically).
Coaxial nanotubes are already experimentally accessible and they indeed show superlubricity.

More info on and discussion of less common concerns here:

Experimental demonstration of superlubric sliders and rotator and vdW suck-in

(wiki-TODO: Add reference to and discussion of paper.)


Pathway concerns

direct path & mixed path

Regarding concerns about atom-by-atom pick-and-place assembly aka piezochemical mechanosynthesis.

  • ED … experimental demonstration
  • TA … theoretical analysis

ED – scanning in 3D (high vertical ledges) is now possible

Coping with high vertical ledges demonstrated possible:
The diamond like surface of a tetramantane molecule (of natural origin)
was subatomically resolvingly scanned while standing upright.
They managed to do this despite the tetramantane molecule being higher
than the picked up CO molecule that was used for imaging.
The method: They took an STM height reference on the gold surface and then
did constant height nc-AFM scanning to get a picture of the top.

Why constant frequency shift scanning is not an option here (and generally rarely):
★ the frequency shift signal of nc-AFM is even more height sensitive than STM
(i.e. nc-AFM features an extremely shallow "depth of fields" in optical analogy terms)
★ coming from the side at surface scanning level would likely
– crash the side of the big fat SPM needle tip apex into the molecule (feedback too slow) or even if no crash …
– pick up the molecule to the side of the SPM needle tip apex due to vdW forces or …
– less likely: scan part of the SPM needle tip apex tip with the tetramantane molecule (reverse imaging situation).
(wiki-TODO: Add a sketch.)

Side-note: The frequency shift in nc-AFM (with qPlus brand sensor) is roughly proportional to
surface stiffness for low excitation amplitudes. Not force as the name AFM would confusingly suggest.
Historic accident. That adding atop there actually being contact possible (rare but possible) despite "noncontact". OUCH!

Remaining challenge: Grater depth of field with focus stacking fusion:
nc-AFM (qPlus brand sensor) has extremely shallow "depth of field" (in optical analogy terms)
Even for a fraction of an atomic step they needed to ramp down the height to see some hidden hydrogen atoms.
This not being automated they where very glad and proud (title of the paper) that they not had to do it again.
Their trick of identification of molecuee species by slant is a special case though.
Needed is a general capability. Needed is automation of things like this height ramping.
More generally we really want automated SPM control to be able to do something that could be called
nc-AFM focus stacking fusion (in optical analogy terms).

Remaining challenge: Stronger attached tool that can not only image but also manipulate:
Note that the standing tetramantane molecule was not picked up, sled around too much for imaging, or tossed over.
That despite there only being a weak vdW bond between three hydrogen atoms and the gold surface.
The scanning is extremely gentle.
For covalent manipulations a picked up CO molecule very weakly bonded to the SPM needle tip apex would not work at all.
Other much more strongly bonded "adapter molecules" are needed. Rabbit hole of design constraints.
Also challenging the current SPM usage philosophy of disposable tip SPM needle tip apex structure.

ED – strong covalent nano-molecular manipulation in 3D

Covalent fusion of a C60 buckyball molecule onto two upwards facing
carbon radicals provided by a graphene nanoribbon that has vertically upward facing parts.
Demonstration that strong covalent bonds can be formed in deeply in 3D way beyond the height of a mono-atomic step.

This is obviously good enough for whole molecule manipulation in a one off demonstration.
Automated reliable usage and more challenging manipulation of single atoms (not counting attached hydrogen atoms)
will need adapter/tool molecules helping in solving solving the problem of the unstable ever changing SPM needle tip apex surface.

ED – SPM manipulations being automateable and scaleable

This was a quite early work.
Still STM only and Cl ad-atons on large scale atomically flat Cu(100) metal.
It did demonstrate automateability and scalability.
The underlying process needs to be switched to new capabilities in
– working up in deep 3D and
– working with strong covalent bonds

ED – elemental identification of element types via force curves

(wiki-TODO: Add reference to and discussion of paper(s).)

To place the right elements at the right spots
one obviously needs to find out what kind of elements are available where of the picking.

In this paper by analysis of the nc-AFM frequency shift curves
they managed to identify the elements {C, Si, Ge, Sn, Pb}
(i.e. the entirety of group14; group of high interest)
present as mixed cover of ad-atoms on the surface Si(111)√3×√3R30°

(wiki-TODO: More details later …)

EDs – progress in atomically resolving nc-AFM on AP nanographenes

Graphene sp2 carbon nanoribbons:

Less flat sp3 carbon too under special circumstances:

Nanoribbons have a problem with termination control in their bottom up synthesis.
But there is progress on this front too:

ED – preserving of tip apex structure during transfer to a different macroscale sample (and back)

(wiki-TODO: Add reference to best fitting COFI paper (& …) and discussion of paper.)

ED – progress with ultra flat surfaces

ED – progress with potential "adapter molecules"

(wiki-TODO: Add reference to and discussion of papers.)

  • several papers
  • transfer paper & conductivity paper

ED – progress in covalent bond formation control (2D for now)

ED – progress in STM control

(wiki-TODO: Add reference to and discussion of papers.)

Early ED (on silicon)

Extraction an re-deposition a a single silicon atom (at 78K) was experimentally demonstrated. This gives experimental evidence for piezochemical mechanosynthesis working.

It was possible to experimentally demonstrate mechanosynthesis of silicon.
Abd that even even with today's still very crude means (meaning blunt tips).
See: Silicon mechanosynthesis demonstration paper or more generally: Experimental demonstrations of single atom manipulation

  • Silicon is a relevant material quite similar in covalent character to diamond.
  • This has been done an reasonable temperatures (meaning not liquid helium but liquid nitogen)

TA – Highly meticulous theoretical analysis (with carbon, a complete system)

It has been shown that the infamous finger problems like …
– the sticky finger problem and
– the fat finger problem
… are not valid.

See: A Minimal Toolset for Positional Diamond Mechanosynthesis (paper)

TA – older theoretical analysis on silicon mechanosynthesis

(wiki-TODO: Add reference to and discussion of papers.)

ED – 4K cryo codeposition of various molecularspecies "garden of molecules"

(wiki-TODO: Add reference to and discussion of paper.)

Incremental path & mixed path

Related

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