Sputtering of tungsten: an atomic view of a near-surface depleted zone created by a single 30 keV /sup 63/Cu/sup +/ projectile. Report No. 4118

The vacancy structure of a near-surface depleted zone (DZ), created by a single 30 keV /sup 63/Cu/sup +/ ion in a tungsten field-ion microscope (FIM) specimen, was determined with atomic resolution. Both the irradiation and pulse field-evaporation experiments were performed in situ at less than or equal to 11 K, so that the observed vacancy structure was unaltered by the long-range migration of self-interstitial atoms. The following basic physical quantities were measured: (1) the number of vacancies; (2) the dimensions; (3) the vacancy concentration; (4) the distribution of first-nearest-neighbor vacancy clusters; and (5) the radial-distribution function for the vacancies out to ninth-nearest neighbor. The values of these quantities were shown to be similar for both the near-surface DZ and DZs created in the bulk of the same specimen by 30 keV /sup 63/Cu/sup +/ projectiles