Trichlorosilane thiol

Herein the focus is on SAMs of trichlorosilanes and thiols. SAMs of carboxyUc acids are important as a connection between the LB and self-assembly techniques, but studies of their formation and stmcture have been relatively limited. SAMs of carboxyUc acids on AI2O2, AgO, and CuO have also been carried out (113—124). 

Patterns of ordered molecular islands surrounded by disordered molecules are common in Langmuir layers, where even in zero surface pressure molecules self-organize at the air—water interface. The difference between the two systems is that in SAMs of trichlorosilanes the island is comprised of polymerized surfactants, and therefore the mobihty of individual molecules is restricted. This lack of mobihty is probably the principal reason why SAMs of alkyltrichlorosilanes are less ordered than, for example, fatty acids on AgO, or thiols on gold. The coupling of polymerization and surface anchoring is a primary source of the reproducibihty problems. Small differences in water content and in surface Si—OH group concentration may result in a significant difference in monolayer quahty. Alkyl silanes remain, however, ideal materials for surface modification and functionalization apphcations, eg, as adhesion promoters (166—168) and boundary lubricants (169—171). 

General Aspects Organic monolayers on well-defined metal substrates may be obtained in various ways. Typical strategies are molecular beam epitaxy (MBE) [436], so-called self-assembled monolayers (SAM) [437] or LB films (LB) [438, 439]. SAM s are molecular assemblies formed by the spontaneous interaction of a surfactant with a solid or liquid substrate. Examples are thiols on gold or silver [437,440,441] as well as alkyl-trichlorosilanes on oxide surfaces [442]. 

Concomitant to the development of the trichlorosilane technique, a method for the chemisorption of monolayers of disulfides on gold was developed by Nuzzo and Allara [25]. It has been rapidly generalized to the adsorption of monolayers of alkanethiols on noble metal surfaces [22,26]. Using acid surface to a copper salt on which another thiol monolayer can adsorb, Ulman and coworkers showed that this chemical self-assembling technique is also useful for multilayers build-up [27,28]. Alternatively a, [Pg.651]

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