Sputter-induced chemical transformation in oxoanions by combination of C60+ and Ar+ ion beams analyzed with X-ray photoelectron spectrometry

Abstract

The change of the chemical states of inorganic oxoanion salts by low-energy single atomic projectiles (0.5 kV Ar(+)), high-energy cluster ion beams (10 kV C(60)(+)), and mixed 0.2 kV Ar(+) and 10 kV C(60)(+) are presented. Although the sputtering conditions of C(60)(+) and C(60)(+)-Ar(+) mixed sputtering used in this work provide more accurate results for profiling organic films than Ar(+) sputtering, the difference in profiling inorganic materials is not as dramatic. For inert oxoanions like carbonate and phosphate, both Ar(+) and C(60)(+) sputtering cause unappreciable sputter-induced chemical transformation to the remaining surface. For reactive oxoanions like nitrate, perchlorate, chlorate, and chlorite, although C(60)(+) yields slightly better results than Ar(+) sputtering due to the thinner disturbed layer, all the ion beams altered the chemical state significantly. As a result, none of these techniques can be used to provide true information below the surface. For intermediate oxoanions like nitrite and thio-S in thiosulfate, C(60)(+) yields slightly better results than Ar(+) sputtering. However, for sulfonate and the core-S in thiosulfate, C(60)(+) causes more sputter-induced chemical transformation than Ar(+) sputtering.