Metallization of self-assembled organic monolayer surfaces by Pd nanocluster deposition

A condensation-cell-type cluster aggregation source was used to deposit Pd clusters on the self-assembled monolayers of four different types of organic molecules. Mica slides covered by Au (111) were coated with self assembled monolayer films of n-dodecanethiol, 4-mercaptopyridine, dimethyldithiocarbamate, and diethyldithiocarbamate, and the behaviour of Pd clusters on these surfaces, as well as on the bare Au (111) surface, was characterized using scanning tunnelling microscopy and X-ray photoelectron spectroscopy. The aim of this study was to present an alternative means for the metallization of organic layers, through the use of preformed clusters that, unlike single adatoms, are less likely to penetrate the organic layer and cause unwanted interfacial layers or short circuits, and deduce its suitability for the various types of organic self-assembled monolayers. Our experimental results indicate that all of the studied self-assembled monolayers are impenetrable for Pd clusters deposited at thermal energies. Contrary to most methods of metallization, Pd cluster deposition therefore provides an efficient means of growing metal overlayers on organic self-assembled monolayers.