Large bubble-like features ordered on a macrolattice in helium-implanted gold

Abstract

IMPLANTATION of metals at temperatures near ambient with helium ions can result in the formation of an ordered array—a superlattice—of small (∼2 nm in diameter) helium bubbles^1–11. The superlattice has the same symmetry as the atomic lattice of the metal but with a lattice spacing about 20 times greater. We now report the observation, in helium-implanted gold, of an ordered array—a 'macrolattice'—of artefacts ∼60 nm in diameter, which we believe also to be helium bubbles. Again, the macrolattice has the same symmetry as the gold lattice, but the lattice spacing is about 400 times larger. The coexistence in a single specimen of three separate lattices of very similar structure but which differ so markedly in scale provides a new perspective on ordering phenomena. In particular, an understanding of the processes that drive bubble ordering may provide more general insight into the development of microstructures in metals during ion irradiation¹². Such information is of value for the production of wear- and corrosion-resistant surfaces by ion implantation^13,14 and the development of materials with appropriate erosion and gas-loading properties for use in future nuclear-fusion reactors^15,16.