Role of chemical bonding in the epitaxial growth of noble metals on ionic crystal substrates

Thin films of Au were deposited onto MgO substrates cleaved in ultrahigh vacuum. The films, which were examined by transmission electron microscopy and electron diffraction, did not grow with a (111) orientation observed in a Au/NaCl system but with a (100) orientation which had been observed in a Pd/MgO system. In order to obtain some insight into the differences in the epitaxial orientations, we studied interfacial chemical bonding states in Au/MgO(100), Pd/MgO(100), and Au/NaCl(100) systems using total pair-potential calculations and discrete variational X alpha calculations. The results show that interfacial interaction in both the Au/MgO and the Pd/MgO system is stronger than that in the Au/NaCl system. The relation between the strength of the interfacial chemical bond and the epitaxial orientation in the above systems is discussed. (C) 1996 American Vacuum Society.