Organometallic chemistry on silicon and germanium surfaces.

This review is about understanding and controlling organic molecular adsorption on silicon. The goal is to provide a microscopic picture of structure and bonding in covalently attached molecule-silicon surface systems. The bias here is that an unprecedented, detailed understanding of adsorbate-surface structures is required in order to gain the control necessary to incorporate organic function into existing technologies or, eventually, to make new molecule-scale devices. A discussion of recent studies of adsorbate structure is presented. This includes simple alkenes, polyenes, benzene, and carene adsorbed on Si(100). Also included is a discussion of wet chemical procedures for forming alkyl and alkoxy covalently functionalized silicon. These discussions are presented together with comments on the related issues of adsorption dynamics and nano-scale manipulation in an effort to point the way toward principles and procedures that will allow the hybrid properties of organic molecules and surfaces to be harnessed.

Controlled molecular adsorption on silicon: laying a foundation for molecular devices.

Advances in techniques for the nanoscale manipulation of matter are important for the realization of molecule-based miniature devices with new or advanced functions. A particularly promising approach involves the construction of hybrid organic-molecule/silicon devices. But challenges remain--both in the formation of nanostructures that will constitute the active parts of future devices, and in the construction of commensurately small connecting wires. Atom-by-atom crafting of structures with scanning tunnelling microscopes, although essential to fundamental advances, is too slow for any practical fabrication process; self-assembly approaches may permit rapid fabrication, but lack the ability to control growth location and shape. Furthermore, molecular diffusion on silicon is greatly inhibited, thereby presenting a problem for self-assembly techniques. Here we report an approach for fabricating nanoscale organic structures on silicon surfaces, employing minimal intervention by the tip of a scanning tunnelling microscope and a spontaneous self-directed chemical growth process. We demonstrate growth of straight molecular styrene lines--each composed of many organic molecules--and the crystalline silicon substrate determines both the orientation of the lines and the molecular spacing within these lines. This process should, in principle, allow parallel fabrication of identical complex functional structures.

Self-directed growth of molecular nanostructures on silicon

Organic functionalization of group IV semiconductor surfaces: principles, examples, applications, and prospects

Recent investigations have shown that cycloaddition reactions, widely used in organic chemistry to form ring compounds, can also be applied to link organic molecules to the (001) surfaces of crystalline silicon, germanium, and diamond. While these surfaces are comprised of SiSi, GeGe, and CC structural units that resemble the CC bonds of organic alkenes, the rates and mechanisms of the surface reactions show some distinct differences from those of their organic counterparts This article reviews recent studies of [2 + 2], [4 + 2] Diels−Alder, and other cycloaddition reactions of organic molecules with semiconductor surfaces and summarizes the current understanding of the reaction pathways.

Cycloaddition chemistry of organic molecules with semiconductor surfaces.

Adsorption and thermal behavior of ethylene on Si(100)-(2 × 1)

The adsorption and decomposition of acetylene on Si(100)-(2×1) have been studied in ultrahigh vacuum by Auger electron spectroscopy, temperature-programmed desorption, and changes in the partial pressure of acetylene as measured by a quadrupole mass spectrometer during the formation of a monolayer. Acetylene was found to chemisorb onto Si(100)-(2×1) via a mobile precursor. The difference between the activation energy for desorption from the precursor and that for reaction from the precursor into the chemisorbed state was found to be (E d -E r )=1.9±0.6 kcal mol -1

Adsorption and decomposition of acetylene on Si(100)-(2×1)

The Adsorption and Decomposition of NH3 on Si(100) - Detection of the NH2(a) Species

A convenient kinetic uptake method has been employed to determine the absolute saturation monolayer coverage of C2H2 and C2H4 on a Si(100)(2×1) surface. Such measurements are important for postulating the structure of the chemisorbed hydrocarbon species on this surface. The saturation surface coverage for both chemisorbed molecules at 105 K is 2.5(±0.2)×1014 molecules/cm2 . This number is consistent with 1 hydrocarbon molecule per Si dimer site at monolayer coverage when the role of surface defects on Si(100) is considered. A di‐σ bonding model for both molecules is proposed at saturation coverage.

P.A. Taylor

Papers

Adsorption and thermal behavior of ethylene on Si(100)-(2 × 1)

Adsorption and decomposition of acetylene on Si(100)-(2×1)

The Adsorption and Decomposition of NH3 on Si(100) - Detection of the NH2(a) Species

Direct determination of absolute monolayer coverages of chemisorbed C2H2 and C2H4 on Si(100)

Chemical activity of the C=C double bond on silicon surfaces