AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP33
Effect of the Sample Topography on the Adhesive Force in Atomic Force Spectroscopy Measurements in Air

Wednesday, October 4, 2000, 11:00 am, Room Exhibit Hall C & D

Session: Poster Session
Presenter: N. Nakagiri, Nikon Corporation, Japan
Authors: N. Nakagiri, Nikon Corporation, Japan
L. Sirghi, Nagoya University, Japan
K. Sugisaki, Nikon Corporation, Japan
H. Sugimura, Nagoya University, Japan
O. Takai, Nagoya University, Japan
Correspondent: Click to Email
It is widely recognized that water thin films formed on probe and sample surfaces greatly affect the atomic force microscopy (AFM) measurements in air. Generally, the interaction between the probe tip and sample surface is a result of superposition of van der Waals, electrostatic, capillary and interfacial tension forces. The latter two forces arise due to water thread usually formed at tip-sample contact region in air and their contribution to the tip-to-sample adhesive force is dominant The effect of local curvature of sample surface on the capillary and interface tension adhesion force of water meniscus formed between AFM tip and sample in air is demonstrated both, theoretically and experimentally. An analytic solution for capillary and tension adhesive force is founded under approximation of thermodynamic equilibrium of a symmetric water meniscus formed at the tip-sample contact region. It is shown that the sample local curvature strongly affects the water meniscus geometry and the adhesion force. Compared to the force computed for a null local curvature of the sample surface, the theoretical model predicts larger/smaller adhesive force for concave/convex local curvature. The theoretical predictions were confirmed by experiment. Atomic force spectroscopy measurements were performed for a silicon nitride cantilever and a standard sample of quartz patterned with 3x3 mm2 in area and 20 nm in depth grooves and platinum covered. Maps of sample surface topography and adhesive force have shown a much small/large force on the high/low part of groove edges, where the sample local curvature is convex/concave.