Chemical and physical interactions at metal/self-assembled organic monolayer interfaces

Abstract

The purpose of research on metals (M) deposited onto self-assembled monolayers (SAMs) is to understand the interactions between metal (M) and eventually metal oxide overlayers on well-ordered organic substrates. Application of M/SAM and inorganic/SAM research results to the understanding of real inorganic/ organic interfaces in vacuum and under environmental conditions can potentially play a key role in the development of advanced devices with stable interfacial properties. The M/SAM approach to interface research is delineated as a new subfield in surface science in the context of other approaches to inorganic/organic interface research. Current issues in M/SAM research are outlined, including chemical compound formation, the morphology (spreading, clustering, or penetration) of the metal species, the kinetics of the metal morphology, the effect of the metal on the degree of order in the SAM, and the rate of metal penetration into the SAM. Probes are recommended that are suitable for M/SAM research. The results of M/SAM studies to date are reviewed, and M/SAM combinations are ranked according to reactivity and penetration. Key probes for addressing gaps in the research results are identified. The effects of defects, disordering, air exposure, and X-ray and electron beam exposure on the experimental results to date are evaluated. Thus far, the results have successfully revealed qualitative relationships of M/SAM chemistry, temperature, and penetration. The chemical interactions that have been found are applicable to real M/polymer interfaces as formed in vacuum. It has yet to be shown that M/SAM research will yield quantitative understanding of interface formation or that M/SAM interfaces are entirely analogous to M/polymer interfaces in the details of interface formation. The future of this subfield of surface science lies in its expansion from M/SAM interfaces in vacuum to other inorganic/SAM interfaces in vacuum and, eventually, under environmental conditions.