SAMs provide a unique link between the science of organic surfaces and technologies that seek to exploit their adaptable character. SAMs are a model system for the study of organic and biological interfaces and are of technical interest for the fabrication of sensors, transducers, protective layers, for lubrication, and as patternable materials. STM effectively tests new types of control over the microscopic structure-property relationships characteristic of SAMs on gold that should prove useful to their application. The ordered dense character of SAMs on gold defines layers in the interface that influence the chemistry, wetting, and transport properties of the surface. Chemistry occurs typically in the region comprising the endgroups.
Wetting is influenced by characteristics of the film associated with a slightly thicker layer.
Access to the underlying gold reflects the barrier properties fo the SAM that are largely the result of the length and organization of the alkyl spacers. Patterning of SAMs combines with the control of their properties to localize the function of the interface at mesoscopic scales. The discovery in 1983 of the self-assembly of disulfides on gold and, soon thereafter, of alkanethiols coincided with the maturation of STM following its invention ine early 80's. SAMs show collective organization of their molecules in at least four phases, constrained by disordered boundaries and substrate defects. The monolayers can also exhibit a type of collective order dominated by end-group packing that overwhelms the substrate topography and generates interfaces with a higher degree of perfection.