From Single Atoms to One-Dimensional Solids: Artificial Gold Chains on NiAl(110)

The tip of a scanning tunneling microscope (STM) was used to assemble well-defined atomic chains from single Au atoms on a NiAl(110) surface. The electronic properties of the chains are determined by a one-dimensional free-electron like band, gradually developing from a discrete resonance state in Au monomers. The adsorption of a single CO molecule on the chain strongly perturbs the electronic structure by suppressing the interaction between neighboring chain atoms. Vibrational properties of the Au/CO adsorption system were obtained from inelastic electron tunneling spectroscopy with the STM, yielding the energy of the hindered rotational mode for Au n CO. The experiments demonstrate the strength of the STM to explore properties of matter in the transition range between single atoms and bulk solids.