Measurements of the polarizability of tungsten adatoms on tungsten (110) planes

It is shown that high quality room temperature field ion images can be obtained. Image contrast can be enhanced by using a Ne-Ar mixture. The enhancement is due to field adsorption of argon at room temperature. Using the room temperature FIM, one can observe the movements of individual adatoms on surface planes. Due to the lateral field gradient existing on surface planes, the adatoms generally are forced to migrate in the direction from the center to the edge of the plane. From the migration speed, the polarizability of the adatoms can be calculated. From our analysis and experimental data, the polarizability of tungsten adatoms on a tungsten (110) plane is found to be 9.2 Å3. A comparison is made to that obtained from field evaporation rate measurements.