The influence of OH groups on the growth of rhodium on alumina: a model study

In order to investigate how the presence of surface hydroxyl groups on oxid e surfaces affects the interaction with the supported metal, we have modifi ed a well-ordered alumina film on NiAl(110) by Al deposition and subsequent exposure to water. This procedure yields a hydroxylated alumina surface as revealed by infrared and high-resolution electron energy loss spectroscopy . By means of scanning tunneling microscopy, we have studied the growth of rhodium on the modified film at 300 K. Clear differences in the particle di stribution and density are observed in comparison to the clean substrate. W hile, in the latter case, decoration of domain boundaries as typical defect s of the oxide film governs the growth mode, a more isotropic island distri bution and a drastically increased particle density is found on the hydroxy lated surface. From infrared data, it can be deduced that the growth is con nected with the consumption of the hydroxyl groups due to the interaction b etween the metal deposit and the hydroxylated areas. This finding is in lin e with photoemission results published earlier.