Fig. 2: Evolution of the chemical and magnetic states of Co nanoparticles deposited on Si/SiOx during in situ oxidation.
From: Absence of a pressure gap and atomistic mechanism of the oxidation of pure Co nanoparticles
a–g X-ray absorption (XA) spectra with increasing molecular oxygen dosage in langmuir (L) (black lines). Specific features at the Co L3 edge of metallic Co and of the different cobalt oxides discussed in the text are indicated in a, c, g. Red dashed lines are fits to the XA spectra. h Relative proportion of Co, CoO, wurtzite-CoO (w-CoO), and Co3O4 as a function of oxygen dosage obtained from a chemical composition analysis. The lines are guides to the eye. i–o X-ray magnetic circular dichroism contrast maps for the different oxygen dosages. The scale bar is 500 nm. The three specific chemical states, A—pristine, metallic state, B—CoO-dominated state, and C—Co3O4-dominated state are denoted in the respective panels. A movie sequence of i–o showing the evolution of the magnetic contrast as a function of oxygen dosage over a larger sample area of 20 μm field of view is available as Supplementary Movie 1.
