Doping of monatomic Cu chains with single Co atoms

Starting from single Co and Cu atoms at a Cu(111) surface we assembled one-atom-wide binary chains of predefined size and composition by atom manipulation in a low-temperature scanning tunneling microscope. We found that the electronic states confined to the nanostructure are quantized. These quantum states, which sensitively depend on the internal chain structure, are described by the Hückel scheme – a simple theoretical approach known from physical chemistry textbooks to calculate molecular orbitals. The present experiment thus can be understood as a situation where individual “artificial molecules” supported on a solid surface are put together from single atoms of a magnetic and a nonmagnetic element.

Three-dimensional representation showing the topography of a nine-atomic chain comprised of three Co and six Cu atoms assembled and imaged in a low-temperature scanning tunneling microscope. Both ends and the center of the chain are occupied by a single Co atom each. The interatomic spacing within the binary chain is 2.55 Å. The Co atoms give rise to a height increase of 10 to 15 pm relative to a pure Cu chain consisting of the same number of atoms.

Jérôme Lagoute, Christophe Nacci, Stefan Fölsch, Doping of monatomic Cu chains with single Co atoms, Phys. Rev. Lett. 98 (2007), 146804.