Selective activation and passivation of nanoparticle catalysts through substrate mediation

Fe nanoparticles are synthesized on a silicon wafer, by the reduction of Fe₂O₃ nanoparticles, through a bonding partner change reaction involving silicon atoms from the substrate. On a silicon surface with germanium nanostructures grown on it, the catalyst particles are selectively activated and passivated. This has been achieved primarily by exploiting the vast differences in the reduction temperature of the oxide particles on silicon and germanium surfaces. We demonstrate this by growing carbon nanotubes selectively interconnecting the germanium nanostructures. The mechanisms of activation and passivation are discussed.