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 An atoms on a Ni-Al(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 AunCO. The experiments demonstrate the strength of the STM to explore proper-ties of matter in the transition range between single atoms and bulk solids.