Quasi atomically precise techniques

Techniques that allow more or less strongly limited creation of atomically precise structures.
They have little (or at best a very minor) use for bootstrapping towards advanced APM systems.
Much of this falls under conventional nanotechnology a term which mostly excludes topics near APM.

Examples:

• Growth of (usually metallic) nanoparticles so small that their atom count is defined
• Shoving together wires with precisely defined lattice and with. Little control on length and endings (see section on usage of TEM for the creation of atomically precise structures below)
• Growth of single walled nanotubes from gas phase / plasma (length and capping usually undefined - results usually mixtures). This is very primitive self assembly with barely any design freedom.

Transmission electron microscopy as atomically precise manipulation tool

Some developments in late 2016 have shown that transmission electron microscopes can be used to convert non atomically precise structures into atomically precise structures. This works only in some specific cases though.

The usually damaging effect of the imaging electrons is exploited probably in the following way:

• The target area is hit strongly localized by the electron beam on high power producing a somehow random result.
• The target area is hit strongly localized by the electron beam on low power to check whether the somewhat randomly resulted configuration fits the desired result.
• If it does the beam is focused to the next spot expanding the sorted atomically precise area
• If it does not not the process is repeated.

Some machine learning might be involved for generating the beam in a shape that is most likely to produce the desired result (details not yet clear to the author of these lines).

• External news link: Fire up the atom forge (video) (TODO: find out some details)

The benefit in comparison to SPM is that it supposedly works naturally in 3D space.

Here's a different method that judging from this concept picture [1] from "2D materials: Metallic when narrow" does allow only very limited control:

• Related paper: "Directing Matter: Toward Atomic-Scale 3D Nanofabrication." [2]
• The technique was used in this work: "Flexible metallic nanowires with self-adaptive contacts to semiconducting transition-metal dichalcogenide monolayers" [3]