X-ray photoelectron spectroscopy investigation of chemical changes to nickel oxide and iron–nickel oxide surfaces caused by monoatomic argon ion and gas cluster ion beam sputtering

Thin films and powders of NiO and mixed Fe–Ni oxides were subjected to ion sputtering using conventional monoatomic argon and a gas cluster ion beam (GCIB; 20 kV, Ar2500 clusters). Partial reduction of Ni2+ to Ni0 was observed in all cases. In mixed oxides, Ni was preferentially reduced compared to Fe. The results indicate that the lower sputter damage often observed for GCIB sputtering of inorganic oxides does not occur for these materials and reinforces that sputter damage must be assessed for specific material systems.