Velocity distribution and yield measurements of Fe ejected from FeS2 during ion bombardment.

Secondary neutrals sputtered by 3-keV Ar+ from FeS2 and Fe were studied by use of laser postionization mass spectrometry and laser-induced fluorescence spectroscopy. The velocity distribution and yield of Fe from the FeS2 sample were measured. The velocity distribution of Fe sputtered from the sulfide is very similar to that of sputtered Fe from the pure metal with both distributions peaking at nearly the same velocity. The yield of Fe from the sulfide target, after prolonged bombardment, was at most 27% of the yield from the metal. The results are compared with Monte Carlo calculations using the TRIM (transport of ions in matter) code. The total sputtering yield of FeS2 was measured using profilometry and was compared with the same measurements of the sputtered metal targets. The surface of the FeS2 was examined by x-ray photoelectron spectroscopy before and after ion bombardment and indicates preferential sputtering of S at low primary ion doses. After prolonged bombardment, the surface becomes similar to that of FeS. The profilometry measurements and the yield measured by mass spectrometry indicate that some of the sputtered Fe is not observed in the neutral ground state; we propose that the unobserved Fe is in the form of clusters.