Surface chemistry of Fe2O3 nanoparticles on ultrathin oxide layers on Si and Ge

In this paper, we report on a comparative study of the effect of Fe2O3 nanoparticles (NP), introduced onto a thin oxide layer formed on silicon and germanium surfaces, on the thermal decomposition pathway of the individual oxide layers. On both the surfaces, NP of Fe2O3 undergo a reduction reaction through a bonding partner change reaction, where the oxygen atoms change from Fe to Si or Ge. On both the surfaces, annealing results in the conversion of the suboxide-like species to dioxide-like species (SiOx to SiO2 and GeOx to GeO2 respectively for Si and Ge surfaces), until the oxide layer decomposes following the desorption of the respective monoxide species (SiO and GeO). Both the Si and Ge corelevels show a larger chemical shift (4.1 and 3.51 eV in Si 2p and Ge 3d corelevels, respectively) for the as-prepared oxide samples with the NP, at room temperature compared to that without the NP (3.7 and 3.4 eV), indicating a catalytic enhancement of the dioxide formation. Selective formation of silicon oxides leads to encapsulation of the nanoparticles and acts like a protective layer, preventing the oxidation of Fe.