Organising Graphene To Self Ordered Arrangement

The manipulation and fabrication of structures on a nanoscale is no small feat. The idea that we are able to control events happening on the scale of atoms is incredible and when it comes to technology there is very little more futuristic than circuit boards made out of just a few atoms. Normally the nanostructure such as the quantum dot or the metamaterial has to be infused into a solid matrix to support it. One common effect that arises is that of misfit stress as represented by the diagram below:

\includegraphics[width=0.7\linewidth]{fig/misfit}
Thank you to the Institute of Microelectronics for this diagram
What has happened is that the yellow crystal lattice (perhaps representing some kind of thin film) does not have the same separation as the substrate’s crystal lattice. When they are forced to align the stress put on the crystal is called the misfit stress. There has been some interesting suggestions about using this stress to manoeuvre nanoparticles for self assembly on the surface of developing crystals. This method has yet to be very successful as it has difficulties producing structures of regular size or even particularly small size.

This study, however, reports the self assembly of carbon nanodots with uniform sizes of about 1.6 nm in diameter with an uncertainty of about  ± 0.2 nm. These were embedded in a boron-carbon-nitrogen alloy. To do this the alloy was grown in a single layer upon an iridium substrate. As the carbon component of the alloy was increased, graphene dots began to appear in the alloy layer which then arranged themselves into an hexagonal pattern. Upping the carbon concentration even more acted to increase the density of the arrays of particles. The uniform size of these nanodots, described as “striking,” is one of the main leaps forward in this study. But of course the controllable periodicity of the nanodot pattern by changing developing conditions is also important. It is believed that this produced material will have unique optoelectronic properties and hopefully further materials of this type can be created in the near future.

Paper links: Self-assembly of ordered graphene nanodot arrays

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