ON THE USE OF THE MICROMARKER TECHNIQUE FOR STUDYING THE GROWTH MECHANISM OF THIN OXIDE FILMS

摘要

The high temperature behavior of microscopic markers, deposited on to pure and ceria-coated nickel, was tested. The markers, having a form of 20-nm-thick palladium bumps with a fractional surface coverage of 0.05 and 30-nm thick gold bumps with a surface coverage of 0.25, apparently interfered with the oxide growth, increasing the oxidation rate on their surface at 973 K over one order of magnitude. As detected by a combination of Auger electron spectroscopy and Rutherford backscattering spectrometry, for ceria modified nickel, the markers' depth-position coincided with the ceria particles dispersed in the vicinity of the oxide-gas interface. For pure nickel oxide films, the markers were easily incorporated into the grow- ing oxide during very early stages of oxidation and were difficult to detect at the oxide-metal interface. It is proposed that the catalytic behavior of the markers was caused by their fragmentation into a large num- ber of islands, leading to the refinement of the oxide grains, which in turn accelerated the substrate oxi- dation rate. Some precautions necessary in conducting the marker experiments are defined.