Measurement of the Polarizabilities and Field Evaporation Rates of Individual Tungsten Atoms

Abstract

The relative field evaporation rates of tungsten kink site atoms at (110) plane edges and the absolute field evaporation rates of individual tungsten adatoms on tungsten (110) planes have been measured covering nine orders of magnitude. From the experimental data, the effective polarizabilities of the tungsten kink site atoms and the adatoms are found to be 4.6 ± 0.6 and 6.8 ± 1.0 ų, respectively. A theoretical consideration is given to explain why the effective polarizability of metal surface atoms depends on the atom‐to‐surface mirror plane distance, and therefore the atomic sites. The calculation also reveals a first power field dependent energy level shift, which is dependent upon the atom‐to‐surface plane distance. It is further shown that the classical image potential no longer holds at a distance smaller than 1 Å from the metal surface.