Monday, January 21, 2008

Two recent ACS papers

Real life is very time consuming. This is a quick post about a couple of cute papers that are up as asap on Nano Letters at the moment.

Coraux et al., Structural coherence of graphene on Ir(111) - This is the first of what I suspect will be a large number of papers coming from people trying to find nice surfaces on which to grow graphene. Sure, it's possible to get graphene over large areas of SiC wafers, as the Georgia Tech group has shown very prettily. Still, for graphene to really come into its own as a technology, it would sure be nice to grow it by some technique like CVD or MBE. These folks have shown that it's possible to grow good graphene over large areas using single-crystal Ir as a substrate. Unfortunately, that's not too useful in and of itself. Still, it's a start, and it lets them look at things like the growth mechanisms and the way graphene accommodates substrate roughness and point defects.

Yang et al., Experimental observation of an extremely dark material made by a low-density nanotube array - This immediately calls to mind the famous line of Nigel Tufnel in This is Spinal Tap, when discussing the cover of their "Black Album": "It's like, 'How much more black could it be?', and the answer is 'None - none more black.'" These folks have been able to use the intrinsic optical properties of nanotubes + the fact that they can be grown in "carpet" form to make the blackest material ever. Pretty cool.


5 comments:

ARL said...

Doug - I am not very familiar with the pros and cons of the different sample growth techniques. Why would it be nice to grow graphene using CVD or MBE?

Doug Natelson said...

Well, right now the two ways to make graphene electronic devices are: (1) Use scotch tape to rub off individual graphene sheets onto a substrate, preferably oxidized Si with a certain thickness of oxide so that the graphene is visible in a phase-contrast optical microscope; (2) Perform a graphitization process at very high temperatures under reducing conditions to convert the carbon-rich face of a SiC wafer into one (usually more) sheet of graphene. Neither of these is too convenient right now, and the latter technique ends up giving you graphene that is effectively doped due to charge transfer from the underlying SiC.

In contrast, single crystal Si can be grown from the melt; polycrystalline Si can be deposited by PECVD. III-V semiconductors like GaAs are routinely grown by MOCVD or MBE (though the latter is slow). What would really be desirable is the ability to grow high quality graphene on, e.g., oxidized Si substrates. Sorry for the brevity of the original post....

sylow said...

I think there are only two groups in the world that can grow graphene by using technique 1 even though it looks incredibly simple. One is Andre Geim in Manchester and the other one is Philip Kim in Columbia. Please correct me if I omited someone Doug.

Masa said...

There are many groups other than Andre Geim and Phil Kim who can make graphene sheets by exfoliation, but rubbing technique is not scalable at all.

Anonymous said...

Nice Spinal Tap reference. You have taken this blog to 11, Doug.