A Method of Determining the Contact Area Between a Particle and Substrate Using Scanning Electron Microscopy

Abstract

A new technique for determining the contact radius between a micrometer size particle and a contacting substrate using scanning electron microscopy has been developed. The Contact Area Measurement (CAM) technique, which is especially suited for small surface-force-induced contact radii, involves evaporating a thin, uniform coating of a conductive material, such as aluminum, over a sample comprised of particles on a substrate while the sample is rotated slowly. The sample is examined before and after particle removal to determine both the radii of the particle and its respective contact. Where the particle contacted the substrate, no metal deposition occurred. The resulting differences in the secondary electron emissions provide a contrast mechanism that the SEM can image. The CAM technique is shown to be useful in examining rigid particles on rigid substrates, where the inherent contacts are small, making measurements difficult, and for examining irregularly-shaped particles and contact areas.

Key Words:

• particle
• contact area
• deformation
• SEM
• adhesion
• polystyrene
• silicon