FUNCTIONAL-GROUP IMAGING BY CHEMICAL FORCE MICROSCOPY

Mapping the spatial arrangement of chemical functional groups and thei r interactions is of significant importance to problems ranging from l ubrication and adhesion to recognition in biological systems. A force microscope has been used to measure the adhesive and friction forces b etween molecularly modified probe tips and organic monolayers terminat ing in a lithographically defined pattern of distinct functional group s. The adhesive interactions between simple CH3/CH3, CH3/COOH, and COO H/COOH functional groups correlate directly with friction images of sa mple surfaces patterned with these groups. Thus, by monitoring the fri ction between a specifically functionalized tip and sample, one can pr oduce friction images that display predictable contrast and correspond to the spatial distribution of functional groups on the sample surfac e. Applications of this chemically sensitive imaging technique are dis cussed.