| New techniques to describe and optimize organization in self-assembled monolayers constructed on solid semiconductor surfaces are reported. Acid-base hydrolytic chemistry of surface anchored [Sn]-NEt2 moieties with alkyne-terminated chromophores has been used to construct close packed thin films of good structural quality on Si(100)/SiO2 substrates. These films exhibit enhanced optical and electrical properties on the surface because of extensive conjugation within the adsorbed molecules, and offer significant potential to develop new nanoscale technologies using tailored properties that meet device purposes.; The discrete surface organization of 1,9-decadiyne and p-diethynylbenzene monolayers on Si(100)/SiO2/SnO2 surfaces is determined with a unique and powerful molecular modelling approach, using rigid geometry scans and periodic geometry optimizations. Geometric arguments produce the monolayer packing space, and rapid optimizations give small, repeating symmetric unit cells that correctly represent an infinite monolayer surface. Semi-empirical analysis of the monolayer symmetry units classifies the infinite thin films as semiconducting materials, because of organized π-orbital overlap and the presence of acceptor bands from the Sn headgroups.; Headgroup bonding is identified as a force for controlling monolayer order. At natural surface packing densities, Sn-O-Sn cross-linking prevents optimal organization of the monolayer because the cross-link distance is smaller than the preferred packing separation of organic chromophores. Optimizations at unnatural surface densities found thin films of lower energy and higher symmetry existed at increased chain-chain separations.; Thin films with adjustable characteristics were created by using binary surface activation units to selectively adsorb different organic molecules. Functionalization of oxide surfaces with statistical mixtures of Si(NR 2)4 and Sn(NR2)4, followed by sequential adsorption of alkynyls at Sn sites, then alcohols at free Si positions, produced randomly ordered films because of unfavourable headgroup interactions. Linking the headgroups, as (NMe2)3SiO-X-C≡C-Sn(NEt 2)3 (X = -(CH2)n-, p-C 6H4-) surface activation units, greatly improves thin film order by preventing phase separation, and increasing average chain-chain distances. Monolayers organize as linear, nanoscale rows and serve as templates for the nucleated crystallization of functionalized chromophores directly from the reaction mixture. Self-generating arrays of highly coloured dendritic crystals, with potential optoelectronic activity, are observed to form directly on solid-state electronic interfaces. |
