STUDY OF PALLADIUM MONOLAYER AND MULTILAYER ON TA(110) BETWEEN 300-K AND 1500-K

Core level photoemission was used to study the growth and thermal modification of Pd films deposited on Ta(110) between 300 and 1500 K. The Ta(110) substrate had Ta 4f core level spectral components which could be identified with the Ta(110) terrace and edge sites. The deposition of Pd causes a 175 +/- 100 meV shift of these surface-related core level components. Little or no additional core level shift is seen when the interface is modified by heating. A decrease in the intensity of the bulk Ta 4f component is observed and is consistent with the growth of a Pd-Ta surface alloy. However, changes in the ratio of the components derived from the edge and terrace sites argue for changes in the size of the Ta(110) terraces due to the preferential growth of the alloy phase at the edges or the development of additional surface facets. These changes in surface morphology appear to be reversed when the Ta substrate becomes hot enough to remove the Pd.