Thermal stability of Co-core-CoO-shell nanoparticles on an ultrathin θ-Al_2O_3 film support

摘要

The effect of annealing temperature on a system of Co-core-CoO-shell nanoparticles on θ-Al_2O_3/CoAl(100) has been investigated using a combination of Auger electron spectroscopy, high-resolution electron energy loss spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy. Results show that thermal treatment leads to a decomposition of the CoO-shell above 450 K, and thus it is strongly diminished with respect to the bulk value. Between 550 and 1050 K the Co particles coalescence and diffuse through the oxide into the substrate. Due to defect recovery, the thermal stability of the thin aluminum oxide film remained unchanged compared to as-grown θ-Al_2O_3.