A Study of Ion Beam Sputtering of Compound Materials with Laser Spectroscopy

Author: Nikzad, Shouleh

Year: 1990

Degree: Dissertation (Ph.D.)

Advisors: Tombrello, Thomas A.; Bellan, Paul Murray

Committee Members: Tombrello, Thomas A.; Goddard, William A., III; Atwater, Harry Albert; Blake, Geoffrey A.; Pellin, Michael J.

Option: Applied Physics

DOI: 10.7907/kgvz-n067

Abstract

Single crystal metal sulfides of ZnS, CdS, and FeS₂ were bombarded with a 3 keV Ar⁺ beam. The secondary neutrals sputtered from the surface of the target were interrogated by laser ionization mass spectrometry and laser fluorescence spectroscopy.

The velocity distribution and yield of sputtered Fe from a FeS₂ sample were measured. The velocity distribution of Fe sputtered from the sulfide is qualitatively the same as that of Fe sputtered from the pure metal. The yield of Fe from the sulfide target, after prolonged bombardment, was at most 20% of the yield from the metal. The results are compared with Monte Carlo calculations using the TRIM (transfer of ion in matter) code. Total sputtering yields of ZnS, CdS, and FeS₂ were measured by profilometry and were compared with the same measurements of sputtered metal targets.

We have demonstrated the necessity of measuring sputtered molecules and excited state neutrals for accurate yield evaluation. The population distribution of ground state multiplets of sputtered Fe from FeS₂ is compared with that measured from an Fe target. The excited state population of sputtered Fe is slightly higher in the FeS₂ target (~10%). Molecular yields have also been measured by laser ionization mass spectrometry from ZnS, CdS, and FeS₂. S is sputtered predominantly as S₂ from all three crystals. Metals are sputtered as the atom, metal sulfide, and metal dimer (except in the case of Fe₂). The yield of the metal sulfidemolecules is about 10% of the yield of the metal. Plausible formation mechanisms of molecules and excited state neutrals are discussed.

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