Sequential adsorption of a cationic polyelectrolyte and individual sheets of the silicate mineral hectorite has allowed controlled, stepwise formation of multilayered films on silicon wafers. Each component adsorbs rapidly by an ion-exchange mechanism, and x-ray diffractometry indicates structural order even in films with thicknesses greater than 0.2 micrometer. The large lateral extent of the silicate sheets (about 25 to 35 nanometers) allows each layer to cover any packing defects in the underlying layer, thus preserving structural order in the growing film. With careful choice of component materials, this method should allow for the preparation of multilayered films with a variety of technologically important properties.

Alkanethiolates in self-assembled monolayers on gold oxidize in air, in the dark, to form sulfinates and sulfonates. The kinetics of oxidation, however, vary depending on the morphology of the underlying gold, with the rate of oxidation increasing dramatically with a decrease in the size of the grains and the amount of Au(111) on the surface. This difference in kinetics of oxidation is sufficiently great that it may provide insight into discrepancies among previous reports in the literature regarding the inertness of these SAMs in air. The oxidized products also desorb readily, and these species decompose under prolonged X-ray irradiation in ultrahigh vacuum.

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Thin gold films placed in contact on compliant elastomeric poly(dimethylsiloxane) supports weld together. This ;;cold welding'' is remarkable both for the low loads required and for the fact that it occurs under ambient laboratory conditions, conditions in which the gold surfaces are covered with films of weakly adsorbed organic impurities. These impurities are probably displaced laterally during the welding. Welding can be prevented by the presence of a self-assembled gold(I) alkylthiolate monolayer on the gold surfaces. The welded contacts have low electrical resistivity and can be made thin enough to transmit light. This system is a promising one with which to study interaction between interfaces.

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