The structure of octadecyl monolayers on the H-terminated Si(111) surface is investigated by molecular modeling simulations, using substitution percentages from 33.3% to 100% of the Si-H moieties by Sialkyl groups. In all calculations, two-dimensionally repeating boxes were used to mimic the modified surface. Calculations without this repeating box approach were shown to be unsuccessful. The results on the repeating boxes showed that only with a substitution percentage of ∼50% is there a good correlation between the structure of the monolayers as obtained from molecular modeling and the available experimental data. A variety of substitution patterns with a substitution percentage of 50% on the Si(111) surface were investigated, which showed that a zigzag-type pattern is most suitable to describe the structure of the layers. From the results of the investigations, an important conclusion for future experimental work is drawn. It is shown that the experimentally determined substitution percentage of 50-55% of the Si-H for Si-alkyl groups is close to the maximum value that can be reached on the H-terminated Si(111) surface.

The possibility to use dilute alkene solutions for the formation of alkene monolayers with 1-hexadecene on a hydrogen-terminated silicon(100) surface has been investigated for a variety of solvents. The resulting monolayers were analyzed by water contact angles. Anisole, n-butylbenzene, and n-decane were found to be unsuitable solvents for monolayer preparation at all 1-hexadecene concentrations used. At high 1-hexadecene concentrations (25% and 10% (v/v)) well-ordered monolayers were formed in toluene, xylene (mixture of isomers), cumene, tert-butylbenzene, and mesitylene. Only with mesitylene are highquality monolayers feasible even at significantly lower alkene concentrations (down to 2.5%), making this the solvent of choice. The newly described procedure reduces the amount of alkene needed to form wellordered monolayers by a factor of 20-40 in comparison with the original procedure that requires neat alkenes.

The formation of soluble reversible coordination polymers with Zn 2+ ions in aqueous solution was studied for two bifunctional ligands, differing in spacer length. Viscosity measurements were used to follow the formation of polymers as a function of the ratio between metal ions and ligands, the total ligand concentration, and the temperature. All the experimental findings could be reproduced and interpreted with a theoretical model that accounts for the formation of chains and rings. At low concentrations and at a 1:1 metal-to-ligand ratio, a large fraction of the ligand monomers are incorporated in small rings, with a small contribution to the viscosity. Rings are less important at higher concentrations or if one of the two components is in excess. The fraction of monomers in chains and rings could be estimated from 1 H NMR measurements, which were in good agreement with the model predictions. With increasing temperature, the fraction of monomers in rings decreases. As a result, the reduced viscosity increases with increasing temperature.

Herein, the influence of silicon surface modification via Si-C(n)H(2n+1) (n=10,12,16,22) monolayer-based devices on p-type 100 and n-type 100 silicon is studied by forming MIS (metal-insulator-semiconductor) diodes using a mercury probe. From current density-voltage (J-V) and capacitance-voltage (C-V) measurements, the relevant parameters describing the electrical behavior of these diodes are derived, such as the diode ideality factor, the effective barrier height, the flatband voltage, the barrier height, the monolayer dielectric constant, the tunneling attenuation factor, and the fixed charge density (Nf). It is shown that the J-V behavior of our MIS structures could be precisely tuned via the monolayer thickness. The use of n-type silicon resulted in lower diode ideality factors as compared to p-type silicon. A similar flatband voltage, independent of monolayer thickness, was found, indicating similar properties for all silicon-monolayer interfaces. An exception was the C10-based monolayer device on p-type silicon. Furthermore, low values of N(f) were found for monolayers on p-type silicon (approximately 6 x 10(11) cm(-2)). These results suggest that Si--C linked monolayers on flat silicon may be a viable material for future electronic devices.

A new approach has been developed to prepare amino-terminated monolayers on hydrogen-terminated silicon surfaces. This two-step procedure is the first method that provides direct control over the surface density of the amino groups. First, a mixed monolayer of a protected ω-amino-1-alkene and a nonfunctional 1-alkene is prepared on a H-terminated Si surface, using either phthalimide or acetamide as NH2-protecting groups. Subsequent removal of the protective groups generates the covalently attached NH2-terminated monolayer, as evidenced from water contact angle measurements, IR spectroscopy, and X-ray photoelectron spectroscopy. Both protecting groups have their own advantages:  use of the phthalimide moiety is synthetically very convenient; the relatively small acetamide moiety can be used to prepare monolayers with high densities (>50%) of amine groups. The reactivity of the amine groups has been confirmed by further modification of the monolayers.