SINGLE-MOLECULE BOND-RUPTURE FORCE ANALYSIS OF INTERACTIONS BETWEEN AFM TIPS AND SUBSTRATES MODIFIED WITH ORGANOSILANES

Recent atomic force microscopy studies have probed specific chemical i nteractions between the tip and the surface. A statistical method that produces information about the magnitude of single-molecule bond-rupt ure forces has been developed in our laboratories. This paper describe s the extension of this technique to the study of single-molecule bond -rupture forces for organosilane coupling agents covalently attached t o hydroxyl-bearing surfaces. Since both the tip and the surface can be modified by functionalized organosilanes, studies of a variety of tip -surface interactions have been possible. We were able to verify the a dsorption of a variety of organosilanes on both the tip and surface us ing X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Interactions that were studied and quantified inclu de van der Waals interactions between bromine-terminated silanes and t he hydrophobic interactions between methyl-terminated silanes on the t ip and surface.