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 C₆₀⁺), and mixed 0.2 kV Ar⁺ and 10 kV C₆₀⁺ are presented. Although the sputtering conditions of C₆₀⁺ and C₆₀⁺–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 C₆₀⁺sputtering cause unappreciable sputter-induced chemical transformation to the remaining surface. For reactive oxoanions like nitrate, perchlorate, chlorate, and chlorite, although C₆₀⁺ 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, C₆₀⁺ yields slightly better results than Ar⁺ sputtering. However, for sulfonate and the core-S in thiosulfate, C₆₀⁺ causes more sputter-induced chemical transformation than Ar⁺ sputtering.