Surface reconstruction - Revision history

Apm: /* Related */ added Thermal decay at room temperature

2021-06-04T09:34:14Z

Related: added Thermal decay at room temperature

← Older revision		Revision as of 11:34, 4 June 2021
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	* [[Seamless covalent welding]]		* [[Seamless covalent welding]]
	* [[Surface diffusion]]		* [[Surface diffusion]]
	* [[Thermodynamics]] <br>Section: Thermodynamics prevents one from having every atom at the place we want it - wrong for practical scales. <br> [[Common misconceptions about atomically precise manufacturing]]		* [[Thermal decay at room temperature]], [[Thermodynamics]] <br>Section: Thermodynamics prevents one from having every atom at the place we want it - wrong for practical scales. <br> [[Common misconceptions about atomically precise manufacturing]]
	* [[Surface passivation]]		* [[Surface passivation]]

Apm: /* Related */ added link to from misconceptions page factored out page: Thermodynamics

2018-08-25T07:41:31Z

Related: added link to from misconceptions page factored out page: Thermodynamics

← Older revision		Revision as of 09:41, 25 August 2018
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	* [[Seamless covalent welding]]		* [[Seamless covalent welding]]
	* [[Surface diffusion]]		* [[Surface diffusion]]
	* [[~~Common misconceptions about atomically precise manufacturing~~]]<br> Section: Thermodynamics prevents one from having every atom at the place we want it - wrong for practical scales.		* [[Thermodynamics]] <br>Section: Thermodynamics prevents one from having every atom at the place we want it - wrong for practical scales. <br> [[Common misconceptions about atomically precise manufacturing]]
	* [[Surface passivation]]		* [[Surface passivation]]

Apm: /* Related */ added link to Seamless covalent welding

2018-08-25T07:38:49Z

Related: added link to Seamless covalent welding

← Older revision		Revision as of 09:38, 25 August 2018
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	== Related ==		== Related ==

			* [[Seamless covalent welding]]
	* [[Surface diffusion]]		* [[Surface diffusion]]
	* [[Common misconceptions about atomically precise manufacturing]]<br> Section: Thermodynamics prevents one from having every atom at the place we want it - wrong for practical scales.		* [[Common misconceptions about atomically precise manufacturing]]<br> Section: Thermodynamics prevents one from having every atom at the place we want it - wrong for practical scales.

Apm: good initial version

2017-07-10T12:37:53Z

good initial version

New page

Atoms on surfaces often reorder into other structures that are different from the internal structure of a solid block of material (aka the bulk).
They do this to minimize energy. For details consult the Wikipedia page and further resources.

If one wants to use [[chemical element|the elements]] of the [[periodic table of elements|periodic table]] like a construction kit then having them self rearrange is obviously rather not very desirable.

== Misleading experimental data ==

Current day UHV systems for nano-science need to be heated to above 200°C (often for hours to days) to drive out rest gas molecules (especially water) that are strongly adsorbed onto the walls.

Out of this reason many material surfaces that actually have sufficient activation energy barriers to prevent surface reconstruction at room temperature have only been observed in a reconstructed state.
Having many images showing reconstructed (annealed) surfaces and view that sow unreconstructed ones can make it seem that almost all surfaces reconstruct which is not necessarily true.

== Preventing / avoiding surface reconstruction ==

Since advanced [[mechanosynthesis]] will be done at room temperature (or more likely below) surfaces with activation energies far above room temperature will not reconstruct.

Just as it is the case with the prevention of surface diffusion one wants to avoid metallic bonds with weak directionality (low energy barriers against angular displacement) instead one wants strong covalent bonds (like in diamond / graphite) or ionic bonds.

Both single crystalline graphite (HOPG) and salt crystals have been imaged in unreconstructed states despite preceding severe heating.

In the case of the [[mechanosynthesis]] of diamond, lonsdaleite, moissanite and related structures one can prevent surface reconstruction by depassivating (hydrogen abstraction) only the spot where the next carbon moiety is planned to be deposited.
Having everything hydrogen passivated in the final product helps keeping surface reconstruction from happening if the product gets heated.

In case of other [[gemstone like compounds]] that contain transition metal elements (like e.g. rutile TiO2 and hematite Fe2O3) there's a strong ionic component beside the covalent bonding component.
{{todo|how much is known about surface reconstruction of these materials '''when not heated'''}}

== Related ==

* [[Surface diffusion]]
* [[Common misconceptions about atomically precise manufacturing]] Section: Thermodynamics prevents one from having every atom at the place we want it - wrong for practical scales.
* [[Surface passivation]]

== External links ==

* Wikipedia: [[https://en.wikipedia.org/wiki/Surface_reconstruction Surface_reconstruction]]
* TU-Wien STM images of NaCl (which does not reconstructed): [[https://www.iap.tuwien.ac.at/www/surface/stm_gallery/nonmetals]]
* TU-Wien STM images of Al2O3 {{todo|find and add link}}