Depth profiling of ultra-thin alumina layers grown on Co(0001)

Epitaxial thin oxide layers were grown by simultaneous aluminum deposition and oxidation on a Co(0001) single crystal, and the metal-oxide interface between the substrate and the grown layer was studied using photoelectron spectroscopy. The oxide layers were composed of two kinds of chemically different layers. Angle-resolved measurements were used to determine the compositions of oxide sub-layers and to reveal their respective thicknesses. The topmost oxide layers were up to 0.23 nm thick, determined by analysis of O 1s and Co 2p(3/2) photoelectron spectra. The results of the analysis show that the interface layer is composed of a mixture of oxygen and cobalt atoms and its thickness is approximately 0.6 nm. The analysis of Co 2p(3/2), Al 2p(3/2) and O 1s core level binding energies confirmed the presence of CoO in the interface layer and Al2O3 in the topmost oxide layer.