Incongruent Sputtering in Nio(100) and CoO(100) with 2 keV Argon Ions

Abstract

ABSTRACTAlthough NiO(100) sputters congruently at 300 K under 2 keV argon ion flux, sputter reduction is observed above a substrate threshold of 350 K. The reduction kinetics are described quantitatively by Fickian diffusion of subsurface oxygen coupled to differential sputtering at the sample surface. Two additional surface oxygen species are detected on sputter reduced NiO by XPS and these species have not been found on either stoichiometric or chemically reduced NiO(100).CoO(100) also shows sputter reduction, although only surfaces that have been pre-annealed to 973 K show significant reduction. Under these conditions, an epitaxial layer of Co3 O4 forms on the CoO substrate and this layer has a threshold temperature to sputter reduction of 550 K. Reduction kinetics for the epitaxy appear similar to those of NiO(100).