SURFACE FORCE MEASUREMENTS ON PICOMETER AND PICONEWTON SCALES

The design of an atomic force spectrometer with force mapping capability is presented and feasibility is demonstrated. The combined technologies of scanning tunneling and atomic force microscopy have been utilized and augmented. Tunnel current control provides the sensitivity for piconewton scale force detection in real space with picometer accuracy. However, the use of a sensitive cantilever beam with a spring constant of the order of 10 N/m or less can be compromised by the precipitous “lever jump” phenomenon during close approach which occurs when the gradient of the attractive potential exceeds the spring constant of the lever. To circumvent this problem a special technique has been developed to control the approach by regulating the probe in a dynamic equilibrium. Preliminary data has indicated the feasibility of this technique. © 1990, American Vacuum Society. All rights reserved.