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Templated Three Dimensional Growth of Quasicrystalline Pb

An international collaboration led by the University of Liverpool has discovered an exotic film of the element lead (Pb), in which the atoms are arranged in pentagonal and decagonal structures rather than in the usual cubic fashion.  Quasicrystals, the discovery of which led to the award of the 2011 Nobel Prize in Chemistry to Dan Shechtman of the Technion Institute, Israel, were first observed in alloyed systems comprising several elements.  

Experiments carried out by a team of researchers in the University’s Surface Science Research Centre have shown that single layers of atoms deposited on quasicrystalline surfaces exhibit the pentagonal and decagonal ordering of the underlying quasicrystal. The lead film was deposited atom by atom and the resulting structure was subsequently recorded by scanning tunnelling microscopy. The experimental observations were found to be consistent with theoretical results obtained by density functional theory.

Dr. Hem Raj Sharma comments:  “What is special about this study is that for the first time, the ordering of lead continues to several layers.  This shows that three-dimensional quasicrystallinity can be observed in lead films.  Since the properties of materials largely depend on the ordering of their structure, this discovery has significant  implications for the uses of these films; Pb is an archetypal superconductor, for example.  It will be of great interest to discover just what are the superconducting properties of this new film”.

This work was supported by the EPSRC Advanced Fellowship of Dr. Sharma, with a team including Prof. Ronan McGrath and collaborators from the National Institute for Material Science in Tsukuba, and Tohoku University, both in Japan. The theory calculations were performed in Chuo University in Tokyo.

The research is published in Nature Communications 4 (2013) 3715

doi: 10.1038/ncomms3715


STM image (50nm x 50nm) after completion of the second Pb layer
STM image (50nm x 50nm) after completion of the second Pb layer
Lead atoms form a film on the surface of AgInYb
Lead atoms form a film on the surface of AgInYb