Composition, structure and morphology of oxide layers formed on austenitic stainless steel by oxygen plasma immersion ion implantation

Oxygen ions were implanted in to austenitic stainless steel by plasma immersion ion implantation at 400 °C. The implanted samples were characterized by XPS, GIXRD, micro-Raman, AFM, optical and scanning electron microscopies. XPS studies showed the presence of Fe in elemental, as Fe²⁺ in oxide form and as Fe³⁺ in the form of oxyhydroxides in the substrate. Iron was present in the oxidation states of Fe²⁺ and Fe³⁺ in the implanted samples. Cr and Mn were present as Cr³⁺ and Mn²⁺, respectively, in both the substrate and implanted samples. Nickel remained unaffected by implantation. GIXRD and micro-Raman studies showed the oxide to be a mixture of spinel and corundum structures. Optical and AFM images showed an island structure on underlying oxide. This island structure was preserved at different thicknesses. Further, near the grain boundaries more oxide growth was found. This is explained on the basis of faster diffusion of oxygen in the grain boundary regions. Measurement of total hemispherical optical aborptance, α and emittance, ? of the implanted sample show that it has good solar selective properties.