A METHOD OF DETERMINING THE CONTACT AREA BETWEEN A PARTICLE AND SUBSTRATE USING SCANNING ELECTRON-MICROSCOPY

A new technique for determining the contact radius between a micromete r size particle and a contacting substrate using scanning electron mic roscopy has been developed. The Contact Area Measurement (CAM) techniq ue, which is especially suited for small surface-force-induce contact radii, involves evaporating a thin, uniform coating of a conductive ma terial, such as aluminum, over a sample comprised of particles on a su bstrate while the sample is rotated slowly. The sample is examined bef ore and after particle removal to determine both the radii of the part icle and its respective contact. Where the particle contacted the subs trate, 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 p articles and contact areas.