September 29, 2011 — Ames Laboratory researchers have discovered very different reactions between various materials and graphene. Rare-earth metals, such as dysprosium (Dy) and gadolinium (Gd), react strongly with graphene, while lead (Pb) does not.

The researchers — Michael C. Tringides, an Ames Laboratory senior physicist; Myron Hupalo, an Ames Laboratory scientist; and Steven Binz, physics graduate student — deposited a few atoms of each element on the surface of graphene, observing the geometry of the atoms’ self assembly via scanning tunneling microscopy.

Lead atoms moved quickly on the graphene surface when cooled, indicating weak electron sharing with the nanomaterial, said Tringides. The dysprosium atoms moved slowly, even after heating, indicating strong interaction with the graphene. Gadolinium had an even stronger interaction.

Images. Rare-earth materials, such as dysprosium (top), behave differently than other materials, such as lead (bottom) when a few atoms are deposited on a graphene and the atoms self assemble.

These findings are the basis of materials selection for graphene-based transistors, which will require metal connections to conduct electricity. Low electrical resistance, thanks to proper metal selection, will support super-fast graphene transistors, Tringides explained.

The rare-earth islands on graphene act as tiny magnets, with very high density. Tringides notes that iron also has a similar high island density. Further research could reveal ways to use metals and graphene for memory architectures.

C.Z. Wang and Kai-Ming Ho, Ames Laboratory theoretical physicists, collaborated on the research, confirming experimental results with calculations on the bonds between graphene and the metals.

Results are reported in the journal Advanced Materials. Access it here: http://onlinelibrary.wiley.com/doi/10.1002/adma.201100412/abstract

The US Department of Energy’s Office of Science funded the research.

The Ames Laboratory is a U.S. Department of Energy (DOE) Office of Science national laboratory operated by Iowa State University. The Ames Laboratory creates innovative materials, technologies and energy solutions. Learn more at http://www.ameslab.gov/