Investigation of partial oxidation of copper deposited on pyrolytic boron nitride

Copper clusters with diameters of approximately 2.0 to 4.0 nm (355 to 2840 atoms) served as models to obtain more detailed information of the complica ted oxidation process of copper surfaces. In addition to the cluster size, the amount of oxygen embedded in the clusters and their structure were chos en as key parameters. SEELFS (surface extended electron energy loss fine st ructure) above the M-2,M-3 edge of copper and HRTEM (high resolution transm ission electron microscopy) were used for the in situ investigations. The c ombination of the two techniques allowed a clear and sound interpretation o f the spectroscopic results. SEELFS measurements on copper clusters prepare d by inert gas aggregation and on clusters primarily oxidised by adding pur e oxygen of different partial pressures to the aggregation gas during the m etal evaporation, i.e., during the nucleating process, were performed. Ther eby a positive shift of the first nearest neighbour distance (FNND) was obs erved when compared to pure copper clusters. This dilatation is caused by o xygen embedded in the clusters. The shape of the FNND peaks indicate heavy distortions within the primarily oxidised clusters. Furthermore, oxygen red uces the fractional amount of multiply twinned particles (MTPs) and the cri tical diameter D-crit for the structural change to fcc in a significant way compared to pure copper clusters.