Long-range interaction of radiation-generated self-interstitial atoms and adatoms on tungsten surface

ABSTRACT

The morphological modification of the W surface induced by specimen irradiation with 5?keV He atoms was studied at the atomic level using low-temperature ?eld ion microscope techniques. The major impact-induced damage mode on W {110} surface was found to be the formation of adatom sets produced by radiation-generated self-interstitial atoms emerging at the surface. The long-range interaction was revealed by evaluating the experimental probability density of finding two radiation-generated adatoms at a given separation in comparison with the probability density corresponding to a random distribution of adatoms. The statistically significant difference of these distributions consists of the absence or severe reduction of observed adatom pairs with separations in the range 5–11?Å. The experimental distribution was characterised by a relatively open arrangement of adatoms with the closest separation of about 11?Å. Our field ion microscope observations also reveal the self-organisation of radiation-generated W adatoms into atomic chains with the lateral interatomic separation substantially larger than the nearest-neighbor distance. These effects indicate the existence of long-range interactions between radiation-generated adatoms and radiation-generated self-interstitial atoms in the subsurface region.