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« Nanoscale Assembly Line Control | Main | State of Global Emergency »

April 10, 2006


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Phillip Huggan

I've just come across this Finnish paper: http://lanl.arxiv.org/PS_cache/cond-mat/pdf/0010/0010096.pdf
It was penned in 2000 and seems to show a simulation of carbon dimer deposition on a carbon terminated diamond (110) surface. That is, not templating on the usually assumed hydrogen terminated surface geometry.

Intuitively to me depositing di-carbon on a carbon terminated diamond surface would result in only more sp2 bonds being created. But this paper seems to suggest more diamond is the product, though I still have to reread it. Is it possible that the basic mechanosynthetic step can be achieved without the need for hydrogen abstraction?!

Chris Phoenix, CRN

Phillip, I think Rob Freitas has been working on dimer deposition simulations on *un*terminated diamond surfaces. I've emailed him a pointer to your comment here.


Chris Phoenix, CRN

Rob Freitas emailed me this, and said I could post it here:

"Thanks Chris. We're already well aware of this work (and many others of a similar nature) -- for instance, we cite Sternberg's final published paper as Ref. 33 in http://www.molecularassembler.com/JCTNPengMar04.pdf. The Sternberg paper is talking about random dimer depositional processess in the context of CVD production of large flat diamond surfaces, not positionally-controlled assembly of precise diamondoid structures. The paper provides useful confirmation that dimers will work well for building on C110, and also confirms some useful barrier heights against surface migration. DMS is very difficult if surface hydrogens are not removed."

Phillip Huggan

Carbon terminated diamond looks like a simpler proof-of-principle dimer deposition. Kind of halfway between some already demonstrated graphite surface reactions and yet to be demonstrated mechanosynthesis on a hydrogen passivated surface. But I think for actually making diamond parts, the greater the hydrogen surface coverage on the diamond surface, the better. Hydrogen passivated diamond surfaces have a higher electron affinity so seem less likely to reconstruct if complex reaction geometries are attempted (I think).

Phillip Huggan

typo: by higher electron affinity I meant to say more surface hydrogen = *more* negative electron affinity.

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