GROWTH MECHANISMS OF MIXED OXIDES ON ALUMINA

In this paper the growth mechanisms of mixed oxides on alumina are exa mined. Two combinations of both LaCeCuO/alumina and MgMnCoO/alumina we re processed by the atomic layer epitaxy (ALE) technique by carrying o ut from five to nine reaction cycles. Each cycle of growth consisted o f the reaction sequences of the corresponding metal beta-diketonate an d air. The layer-by-layer growth was followed by element determination s and FTIR spectroscopy. X-ray diffraction (XRD), scanning electron mi croscopy with elemental mapping (SEM-EDS) and surface area measurement s were carried out on the mixed oxides after the growth was completed. It was shown that mixed oxides can be processed on alumina in a repro ducible fashion by ALE using the metal beta-diketonates as precursors. Owing to the high alumina surface area, a submonolayer of atoms bound on a surface could be precisely determined and the growth rate follow ed stepwise after each reaction sequence. In addition, during the grow th, the stability and also the tendency of the metal beta-diketonates to etch the oxide layers could be evaluated. Although etching played a n important role in the growth, it was also found to be reproducible. On the whole, it is suggested that the growth on high surface area mat erials can be used as a tool to deepen our understanding of the growth mechanisms involved in ALE.