Ion fluence dependence of the total sputtering yield and differential angular sputtering yield of bismuth due to 50Â keV argon ion irradiation

The dependences of the total sputtering yield of Bi and the differential angular distribution of these sputtered Bi atoms on the fluence of 50 keV Ar+ ions at normal incidence have been experimentally measured. Polycrystalline Bi targets were used for these purposes. The collector technique and accurate current integration methods were adopted for the determination of angular distributions of sputtered Bi atoms. The ion fluence was varied from 1.9 × 1019 to 3.1 × 1020 ions/cm2. The sputtered atoms were collected on high purity aluminum foils under ultra-high vacuum (∼5 × 10−9 Torr). The collector foils were subsequently analyzed using heavy ion Rutherford backscattering spectroscopy. The shape of the angular distribution of sputtered atoms was found not to change significantly with the fluence, but the sputtering yield increased significantly from 2.2 ± 0.2 to 9.6 ± 0.6 atoms/ion over the fluence range studied.