Sputtering of Molecules From ZnS, CdS, and FeS2

Abstract

It has been the general consensus in the sputtering community that molecules are sputtered from a clean metal surface in much smaller quantities than atoms. Some of the existing models further suggest that the sputter yield of molecules should be even lower from a compound than from a pure metal when the constituents of the molecule do not reside on neighboring sites in the solid.In our experiments, neutral species sputtered from single crystals of ZnS, CdS, and FeS2by a 3 keV Ar+beam have been observed by laser photo-ionization followed by time-of-flight mass spectrometry. While the atomic metal (Fe, Zn, Cd) and S2were the predominant species observed, substantial amounts of S, FeS, Zn2, ZnS, Cd2, and CdS were also detected. The experimental results demonstrate that molecules represent a larger fraction of the sputtered yield than was previously believed from secondary ion mass spectrometry experiments. In addition, our data suggest that the sputtered molecules are not necessarily formed from adjacent atoms in the solid. The applicability of various sputtering models will be discussed in the light of these results.