Friction force microscopy: towards quantitative analysis of molecular organisation with nanometre spatial resolution.

Friction force microscopy (FFM) is a technique based upon scanning force microscopy that provides information on the properties of molecular materials. Continuum mechanics provides models that may be used to conduct quantitative analyses of data. While there are some important unresolved issues associated with the contact mechanics of the tip-sample interaction, there is a growing body of data that demonstrates the sensitivity of FFM to changes in molecular organisation and surface composition. Importantly, FFM provides these data with nm spatial resolution, making it in many respects a unique tool for exploring the structures of organic materials on small length scales. Some of the capabilities of FFM are illustrated by drawing on both the literature and work performed in the authors' laboratory on self-assembled monolayers. For example, the compositions of mixed monolayer systems may be determined, with control of tip chemistry providing an additional element of chemical specificity; the alkyl chain organisation may be investigated; and the rates of surface chemical reactions may be measured. FFM is a powerful tool for the quantitative investigation of nm scale chemistry.