
Theory Meets Material Science - joeyespo
https://rjlipton.wordpress.com/2016/05/09/theory-meets-material-science/
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rsfern
I found this summary a bit hard to follow, so I read the 2008 Nature paper the
author refers to [0]. (It's behind a paywall, but the supplemental materials
in [1] are available.) It seems like Silicium is using an approach that's
similar in concept, but there's not a lot of technical detail in this blog
post. Presumably that's because they are trying to commercialize their
research.

The topic is engineering more effective thermoelectric materials -- they
generate an electric potential when subjected to a thermal gradient. Here you
want a high electronic conductivity and a low thermal conductivity, which is
hard to achieve because electrons transport heat very effectively.

The approach outlined here is to use an array of doped silicon nanowires
instead of a bulk material. They make the nanowires thinner than the phonon
mean free path, which essentially confines the dominant heat transfer
mechanism (lattice vibrations) in this system to one dimension. The nanowires
are thick enough that the nanowire array still has electronic properties
similar to bulk silicon, so you can get a lower thermal conductivity without
sacrificing electrical conductivity.

The programming::materials design analogy at the end of the blog post is
interesting. This is actually one of the core philosophies of materials
science -- (hierarchical) materials structure (and chemistry) dictates
physical properties, and is highly dependent on processing and fabrication
routes. You engineer materials with more desirable properties by manipulating
their structure. The hard part is learning reliable structure-->properties and
processing-->structure mappings.

[0]: doi:10.1038/nature06458 [1]:
[http://www.wag.caltech.edu/home/jamil/Nature-SiNWs-TE-
supple...](http://www.wag.caltech.edu/home/jamil/Nature-SiNWs-TE-
supplement.pdf)

