Interfacial force microscopy is a novel technique for imaging and quantitative determination of the mechanical properties of a material such as elastic modulus, hardness, etc., with nm spatial resolution and nN force resolution. Due to the extreme pressures generated during probe-surface contact (many GPa), passivation of the chemical interactions, specifically adhesion, between the parabaloidal tungsten probe tips (radii 35≪r≪200 nm) and the substrate under investigation is often required. Convenient and effective protective monolayers are not generally available for many substrates, and it is necessary to develop a general procedure for passivation of the tip. We have derivatized tungsten(100) surfaces with the silane coupling agent (octadecyltrichlorosilane, OTS) and applied the same techniques to nm-scale tungsten tips. Force versus displacement (f–d) curves were recorded for the following tip–substrate interactions: underivatized tungsten tip against underivatized Au(111) surface, underivatized tungsten tip against derivatized Au(111) surface (C-18 thiol SAM), and derivatized tungsten tip (OTS) against underivatized Au(111). The data clearly show that the OTS derivatized tips were passivated against adhesive contact even at pressures of many GPa, thereby demonstrating the stability necessary for use in nanoindentation experiments. © 1999 American Vacuum Society.