Experimental studies of the behaviour of single adsorbed atoms on solid surfaces

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Abstract
The behaviour of single adsorbed atoms (adatoms) on solid surfaces can now be studied with the field ion microscope (FIM) and the atom-probe FIM. With the FIM, adsorbed atoms can be seen. With the atom probe, adatoms can be analysed. The substrate surface for experimentation can be developed to atomic perfection by low-temperature field evaporation. The number of adsorbed atoms participating in an experiment can be specified and controlled. Quantitative information on diffusion parameters, interatomic forces between adsorbed atoms, adatom-impurity-atom interactions and adatom-plane-edge interactions, etc, can be measured. Association of single atoms into clusters and their dissociation, and the information of adsorption layer superstructure, can also be studied in atomic detail. The charge distribution of a surface atom or the localised electronic density of states of an adatom, can be studied by measuring both its dipole moment and polarisability. Basic principles and results of these FIM studies with single atoms are presented and discussed. Possible future studies are also considered, and their principles described.