Investigations of Surface Processes with the Atom‐Probe Field Ion Microscope

Abstract

Abstract Field ion microscopy ranges from the study of lattice defects to biomolecules. The atom‐probe adds versatility by permitting the mass spectrometric identification of single atom spots selected by the observer. Noble image gas atoms are found to be adsorbed at the specimen surface under normal operating conditions of the FIM. Binding energies are derived and a new mechanism of field ionization by electron tunneling through the adsorbate atom is evidenced. In the presence of the field the substrate metal forms surface molecules with noble gases as well as with the common gases, while field‐induced dissociation of adsorbed CO is also established. A modified atom‐probe with partial retardation permits discrimination of energy deficits of field evaporating species from satellite signals due to hydride formation. Ion energy deficits are mostly caused by premature field evaporation, while the losses due to excitation of surface plasmons as suggested by Lucas do not seem to have the predicted magnitude.