Secondary Ion Mass Spectrometry analysis of metal oxides using 70 keV argon, carbon dioxide and water gas cluster ion beams

Manganese (II) oxide (MnO), manganese (IV) oxide (MnO2), cobalt (II,III) oxide (Co₃O₄) and nickel (II) oxide (NiO) were analysed with time-of-flight secondary ion mass spectrometry using 70 keV gas cluster ion beams. The obtained mass spectra are influenced by projectile chemistry and to a lesser extent velocity. Gas cluster ion beams containing CO₂ or H₂O enhanced the relative yield of metal oxide and metal hydroxide secondary ions compared to beams containing only Ar. For all gas cluster ion beams tested, steady state ion ratios [M_xO_y]⁺/[Mx]⁺ were reached. For manganese oxides, the [MnxOy]+/[Mnx]+ ratio reflected the metal oxidation state whereas the [Mn_xO_yHz]⁺/[Mn_x]⁺ ion ratios did not. This study demonstrates that Secondary Ion Mass Spectrometry using 70 keV gas cluster ion beams provides a novel approach to the quantitative analysis of the surface and sub-surface regions of metal oxides related to energy-storage materials.