May 2, 2008
Nanowiring using boron clusters
A model system that could serve as a "blueprint" for graphene-based nanodevices of the future has been put forward by scientists in Italy, Turkey and Germany. The model involves using alternating chains of boron clusters to connect various parts of a semiconducting graphene substrate. The concept is very similar to that routinely employed in silicon-based integrated circuits, but the resulting graphene-based devices would be several orders of magnitude smaller.
Graphene is set to become one of the key materials in future nanotechnology applications. However, graphene-based devices studied so far are on the micron rather than nanoscale because they mainly consist of broad sheets of graphene connected by wiring of about the same size.
Now, Jens Kunstmann of the Max-Planck Institute for Festkörperforschung in Stuttgart and colleagues have proposed a way to take the wiring down to the nanoscale by implanting chains of B7 clusters into the graphene matrix. These clusters might then be used to connect various areas of a semiconducting graphene substrate.
Previous theoretical studies on heterogeneous nanotubular boron-carbon networks by the team have shown that boron and carbon are compatible on the nanoscale. The researchers have gone a step further and calculated that small planar boron clusters embedded into a graphene substrate act as metallic islands. These functionalize the surrounding graphene to allow electron transport through the substrate.
So could the concept be applied to real systems? "Implantation of boron clusters into bulk silicon is already an industry standard," explained Kunstmann, "so why not try the same treatment for graphene? We examined an alternating chain of boron clusters, where individual clusters are separated by pieces in the underlying carbon matrix."
"As well as technological applications, boron-functionalized carbon might also serve as a challenging test case for state-of-the-art nanotechnology," he told nanotechweb.org.
Kunstmann stressed that his team's preliminary results should not be overrated and said he would like other theorists to join in and advance the study of functionalized graphene. "Here, it might be most interesting to find out about the nature of the electronic transport through these boron wires," he said. "We clearly see electron states appearing in the gap of the underlying graphene, but this does not tell us anything about the basic transport mechanisms in such materials."
He also added that in realistic nano-layouts, the boron chains might be irregular, containing clusters of different sizes and shapes. "So what are the physical and chemical limitations here, and where would the basic functionalization by these boron chains finally break down?" he asked.
The work was reported in arXiv.
About the author
Belle Dumé is contributing editor at nanotechweb.org