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August 13, 2003

It’s a Wonderful World

The world is weird and wonderful place.

A few recent bits of evidence:

Posted by distler at August 13, 2003 12:30 PM

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Re: It’s a Wonderful World

Hi Jacques,

I’m a PhD student working at the University of Exeter in the U.K., specifically performing ab-initio calculations on defects in diamond.

I’ve been following your weblog, almost daily, for quite a while now, and after reading “Diamonds are a geek’s best friend”, I finally feel qualified enough to venture a comment.

Alas, I can’t think of anything to say. Maybe something will come to me.

Many thanks for your time.
:]

Posted by: Steve Sque on August 14, 2003 6:28 AM | Permalink | Reply to this

CVD

Glad you are enjoying this blog. And here I though only web-spiders were visiting my site :-).

Anyway, if you have any insights into the CVD process used by the Boston company (Apollo Diamond), please add a comment.

While I thoroughly relish the thought of breaking the back of the De Beers cartel, the really exciting prospect is for diamond-based integrated circuits. A one foot diameter wafer of pure diamond really is a geek’s best friend.

Posted by: Jacques Distler on August 16, 2003 12:57 AM | Permalink | Reply to this

Re: CVD

Well, as a newcomer to the field, and a theorist at that, I presently know very little about the CVD process, although I can state that the wired article has certainly been ‘sexed up’ (as the media here in the U.K. might put it) for the general audience. And Apollo Diamond are certainly not the only group capable of producing single-crystal CVD diamond, patent or not.

I can however comment on the “diamond-based integrated circuits” side of things. I have recently been working on the n-type conductivity problem in diamond. Now, we know that p-type conductivity is not (much of) a problem, due to substitutional boron having a ‘low’ activation energy of 0.38 eV in diamond.

However, the situation with regards to a suitable dopant for n-type behaviour is not so straightforward.

Nitrogen is readily incorporated into diamond, but has a deep donor level — its activation energy is about 1.7 eV.

Phosphorus doping of diamond has been an encouraging success story — It has taken nearly 10 years, but at least two groups (Japan, Belgium) can now claim 100% reproducibility in doping diamond with P and getting n-type activity with an activation energy of 0.6 eV. Some nice pn—junctions have been successfully fabricated from boron-doped and phosphorus-doped diamond by both of these groups.

Sulphur as an n-type donor has had a controversial history, with experimental and theoretical groups putting its donor level all over the place. Also, one of the first groups to report n-type activity with sulphur-doped diamond was later exposed as having been working with diamonds with non-negligible concentrations of boron, and that the activity was in fact p-type.

Now, my modelling calculations using density-functional theory predict that arsenic and antimony will have donor levels shallower than P, with activation energies of about 0.3—0.4 and 0.2—0.3 eV respectively. This follows from a simple argument treating the donor electron as experiencing a hydrogen-like (effective mass) potential, and with an increasing orbital radius as the atomic number of the dopant atom increases N, P, As, Sb…

Incidentally, my calculations predict sulphur (and singular S—H) to have a relatively deep single-donor level.

The problem with As and Sb doping lies (arsenic poisoning notwithstanding) in getting these large impurity atoms into the diamond lattice. However, even P has a negligible theoretical bulk solubility in diamond, but it is know to be readily incorporated into ⟨111⟩ growth sectors, via a mechanism that is currently not understood. Maybe As can undergo the same process, be incorporated into the bulk, and act as a shallow donor?

Mentioned in the article is a “novel way of inverting boron’s natural conductivity” in order to get n-type behaviour. This surely refers to the work by Teukam et al. on deuterated boron, recently published in Nature Materials. Now my calculations, and those of others in my group on hydrogenated boron defects in diamond do not support these claims, and indeed there is a lot of scepticism in the community concerning this paper.

So, to sum up, there’s a little way to go yet.

PS. When I visit your pages and see some ‘proper’ theory, I stop calling myself a theorist and use ‘modeller’ instead.
:o)

Posted by: Steve Sque on August 18, 2003 8:44 AM | Permalink | Reply to this

Re: CVD

Thanks for the followup! this is really helpful.

I can state that the wired article has certainly been “sexed up” (as the media here in the U.K. might put it) for the general audience.

A shocking revelation!

I have recently been working on the n-type conductivity problem in diamond.

Which is why I love blogging! Link to an intriguing popular article and who writes back, but an expert on the very subject of interest.

Now, we know that p-type conductivity is not (much of) a problem, due to substitutional boron having a “low” activation energy of 0.38 eV in diamond.

However, the situation with regards to a suitable dopant for n-type behaviour is not so straightforward.

Yep, that much was pretty clear from the article. From your description, people have already had success with Phosphorus, and Arsenic may be very promising (I wouldn’t worry about the health aspects; semiconductor fabrication is already a pretty noxious process).

Mentioned in the article is a “novel way of inverting boron’s natural conductivity” in order to get n-type behaviour. This surely refers to the work by Teukam et al. on deuterated boron…

Cool! I couldn’t make heads or tails of that passage. But, from your comments, it sounds a little dodgy anyway.

Posted by: Jacques Distler on August 18, 2003 10:43 AM | Permalink | Reply to this

Re: It’s a Wonderful World

QUOTE:”Glad you are enjoying this blog. And here I though only web-spiders were visiting my site :-).”


HaHa. It’s definitely not only spiders visiting this blog :)


I’m going to try to find your RSS feed and subscribe. I’ve always been fascinated by the CVD process.


Re: the famous Wired article, I think DeBeers can take care of themselves… The Blood Diamond movie was a much bigger threat to the diamond industry than Apollo or Gemesis. And besides GM who succeeded in the 50’s, and DeBeer’s internal research group…with rumours of great successes that were only pursued for academic interest…there are others who worked on the man made diamond…but one way or another, the natural diamond never had to deal with a serious alternative the way Emeralds did. And I think unless it becomes so easy and inexpensive to make a gem-quality diamond that any small lab can do it, this is a threat that will be contained for quite some time…

For better or worse…

Posted by: GilbertZ on April 12, 2007 7:43 AM | Permalink | Reply to this

Re: It’s a Wonderful World

The tool making crow is incredible! I first came across this remarkable bird in an excellent presentation by Joshua Klein. He’s actually been working on the development of a “vending machine” for Crows. If I understand correctly, he believes that with some simple and incremental training we can redefine our relationship (human to crow) with these highly intelligent birds. You can see his presentation at TED here: http://www.ted.com/talks/lang/eng/joshua_klein_on_the_intelligence_of_crows.html

If you have 15 minutes to burn sometime, this video will make you think about crows in a completely different light.

It is indeed a wonderful world.

Posted by: Sarah Mascot on January 25, 2010 1:44 AM | Permalink | Reply to this

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