(ArO)+ and (ArO2)+ ions in rf sputter deposition discharges

Abstract
Glow discharge mass spectrometry was used to study the occurrence of argon–oxygen ions in rf‐diode sputter deposition discharges. The results show that (ArO)+ and (ArO2)+ ions are formed over an extensive range of Ar–O2 sputtering gas mixtures. The populations of these ions are independent of whether a ZnO or Au target is used and coupled in a manner that indicates (ArO2)+ is formed first then dissociates to form (ArO)+. An associative ionization reaction between an Ar atom in a highly excited long‐lived Rydberg state and ground state O2 is proposed to be responsible.