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This paper describes the oriented nucleation of calcite controlled by self-assembled monolayers (SAMs) of ω-terminated alkanethiols (HS(CH2) n X) supported on metal films. The effect of the chemistry and geometry of the organic surfaces was surveyed by using different functional groups (X = CO2 -, SO3 -, PO3 2-, OH, N(CH3)3 +, CH3) and different supporting metals (Au and Ag). Optical microscopy, SEM with image analysis, and XRD were employed to characterize density and orientation of the crystals. Compared to the control surfaces of bare metal films, SAMs terminated in CO2 -, SO3 -, PO3 2-, and OH groups were more active in inducing nucleation, whereas SAMs terminated in N(CH3)3 + and CH3 inhibited nucleation. The crystallographic orientations of the crystals were distinct and highly homogeneous for each surface, but different on different surfaces. SAMs of CO2 -/Au, CO2 -/Ag, OH/Au, OH/Ag, SO3 -/Au, and SO3 -/Ag induced the face-selective nucleation of calcite from the (015), (012), (104), (103), (1 0 12), and (107) crystallographic planes, respectively. SAMs of PO3 2-/Au and PO3 2-/Ag were specific for a family of planes that form an angle of 24° and 40° with the c-axis, respectively. The high degree of orientational uniformity of the overgrown crystals (97−100% oriented crystals for well-ordered SAMs) and the decrease of uniformity as the defect density in the SAMs increased imply that nucleation takes place from the oriented, homogeneous SAM and that the specific interfacial structure is controlling orientation of crystal growth. The possible correlation between the differences in the structure of SAMs supported on Au and Ag and the orientation of the incipient crystals is discussed. Varying the geometry, chemistry, and pattern of the functional groups on SAMs provides, therefore, a tool for a fine-tuning of the orientation of crystal growth and for the formation of high-resolution patterns of oriented crystals.

Monolayer films of several primary substituted hydrocarbons CH3(CH2) n CH2X (X = CH3, OH, NH2, SH, Cl, Br, I; n = 16−30) have been imaged on graphite at the solution−substrate interface using a scanning tunneling microscope (STM). The straight chain hydrocarbons form well-ordered 2-D films on graphite and physisorb with their molecular axes parallel to the surface. The NH2, SH, Br, and I end groups are observed as bright spots in the STM image corresponding to an enhancement in the tunnel current in the vicinity of the functional group, relative to the remainder of the carbon chain. On the other hand, the OH and Cl substituents were not distinguishable from the alkyl chain in the STM images. Comparison of the relative “brightness” of the functional groups with respect to the carbon chain reveals an empirical relationship between increasing relative brightness and increasing molecular polarizability. A model is proposed to describe the STM imaging mechanism for these insulating, physisorbed films in which the role of the adsorbate's polarizability, electronic structure, and orientation with respect to the surface are considered.

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This paper describes the development of a new methodology, “topographically directed etching” or TODE, that relies on patterned regions of disorder in SAMs to generate features specifically at the edges of topographically patterned metal films. The features that are produced have lateral dimensions of <50 to 200 nm and are at least an order of magnitude smaller than those patterned originally in the material, when the original patterning is at the scale of μm. Several variations of this methodology are described, the results of which include the generation of 100-nm trenches in silver, gold, SiO2/Si, and Al2O3/Al, 100-nm lines of silver, asymmetric structures in aluminum and silver, and 50-nm features in curved silver surfaces. Although the techniques can be combined with photolithography, the pattern transfer step is based on chemical reaction and is therefore not limited by diffraction or depth of focus. This methodology makes the fabrication of ∼100-nm structures accessible to chemists/materials scientists without access to tools required for electron-beam writing and other procedures of nanofabrication.