SURFACE-CHEMISTRY AND TIP SAMPLE INTERACTIONS IN ATOMIC-FORCE MICROSCOPY

Microfabricated silicon nitride cantilevers with integral tips are commonly employed in atomic force microscopy. The link between surface chemistry, including surface group acid-base dissociation and counterion complexation, and tip-sample interaction in aqueous electrolyte solution is examined. Silicon nitride tip interaction with ''flat plate'' samples of both muscovite mica and silicon nitride as a function of aqueous solution pH and electrolyte concentration is investigated. The long-range component of the interaction is normalized with respect to an effective tip radius, and as a result electrical double layer and van der Waals interactions can be discussed quantitatively. Microfracture and tribochemical tip wear is also discussed with reference to atomic force microscope contact mode imaging. Non-retarded Hamaker constants are reported for a range of silicon nitride, silica, silicon and muscovite mica systems.