Low-temperature STM/STS investigation of nanostructures created by an STM tip on Au(111) surfaces

We have investigated the electronic structure of atomic size particles on clean Au(111) surfaces by means of scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) at low temperatures. Au adatoms were created on Au(111) with high reproducibility by bringing the STM tip in (near) contact with the surface, providing a rather easy means of creating larger nanostructures out of atomic size particles. Scattering of Au(111) surface state electrons at the adatom site gives rise to the formation of complex standing wave patterns. The electronic structure of the adatoms appears to be dominated by a pronounced resonance below the onset of the Au(111) surface state. The observed resonance is interpreted as a bound state that is split off from the 2D surface state of the Au(111) surface.