SCANNING FORCE MICROSCOPY CHARACTERIZATION OF LANGMUIR-BLODGETT-FILMSOF SULFUR-BEARING LIPIDS ON MICA AND GOLD

Physisorbed and covalently bound Langmuir-Blodgett (LB) monolayers of sulfur-bearing lipids on mica and on gold substrates, respectively, ha ve been studied. Scanning force microscopy, in topography and friction modes as well as in contact and noncontact modes have been used to in vestigate these films in the region of coexisting phases. For the firs t time, a detailed and complex internal structure of solid-analogous m onolayer domains, reflecting their symmetric morphology, has been obse rved. Comparisons of physisorbed monolayers on mica with chemisorbed m onolayers on gold show distinct differences in the structure and stabi lity of the films caused by the different substrate/film interactions. It is found that the use of a substrate to which the film can bind co valently does not result in changes to the morphology of solid-analogo us domains in the films. The structure of covalently bound monolayers is well-preserved over long time periods and is stable at solid/fluid interfaces. However, the covalently bound LB monolayers are more susce ptible to damage by the SFM tip than the physisorbed films on mica.