ABSTRACT
This paper is an extension of recent research1' 11 to elucidate penetration rates of metal overlayers through self-assembled monolayers (SAMs) using ion scattering spectroscopy (ISS)6'7 or to identify metal/organic functional group interactions at metal/SAM interfaces, primarily by means of X-ray photoelectron spectroscopy (XPS).1'5’8' 11 As illustrated in Fig. la, SAMs have fulfdled a need for model systems with ordered organic surfaces of uniform chemical composition for studying interactions at metal (M) or metal oxide (MO)/organic interfaces.1' 11 In principle, atomically sharp interfaces can be formed between the deposited overlayer and the SAM surface. Chemical bonding at metal/organic interfaces plays an important role in the reliability and durability of many technological devices.12 Bonding at organic/metal or organic/metal oxide interfaces typically has been studied either by surface analysis of organic species adsorbed onto single-crystal metal surfaces,13’14 or by coating a metal oxide with a polymer, whereas metal/organic interfaces have been
Fig. 1. (a) Idealized scheme for using an organized molecular assembly to form an interface between a metal overlayer and an organic functional group. The thickness d of the SAM is the length of the molecule at perpendicular attachment. For alkanethiol SAMs on gold, the attachment group is a thiolate, and the methylene chain is 28° from the normal at 295 K; (b) cross sections of the principally observed results to date in which there is a (S) strong metalOFG interaction, (C) weak metal-OFG interaction, or (P) very weak metalOFG interaction. The designations S, C, and P stand for smooth, clustered, and penetrating, respectively.
