Design and calibration of a scanning force microscope for friction, adhesion, and contact potential studies

Abstract

We present the design and calibration of a scanning force microscope which can be used to study friction, adhesion, and contact potential differences between the cantilever tip and surface. The microscope uses a modular design where the laser, cantilever/sample holder, reflecting mirror, and detector are mounted directly on an optical table. The laser, reflecting mirror, and detector are mounted on translation and rotation stages. With this design the components can be rearranged to calibrate the Z piezo motion as a function of applied voltage. Using the detector micrometers, the detector response (voltage-to-distance relationship) can be determined after each series of measurements. The cantilever/sample holder is constructed such that the components are material matched and thermally compensated from a common reference point. This design feature minimizes thermal drift of the instrument. The instrument can be used in a contact scanning mode where both normal and lateral deflections of the cantilever are measured. In addition, the instrument can be used in frictional force studies, force curve mapping of the surface, and contact potential measurements. We present examples of each, including a detailed account of the instrument design and calibration.