CONDUCTANCE STEP FOR A SINGLE-ATOM CONTACT IN THE SCANNING TUNNELING MICROSCOPE - NOBLE AND TRANSITION-METALS

Conductance steps for atomic point contacts of An, Ni, and Pt have bee n measured. Jump-to-contact and jump-to-tunnel processes have been ide ntified and their conductances measured. Differences between conductan ce steps for noble and transition metals are interpreted as being due to the d orbitals that, in transition metals, provide new channels to the electron conductance. This interpretation is supported by a theore tical analysis, which shows good agreement with the experimental data.