Adhesive force of the microstructures measured by the atomic force microscope

Abstract

A technique for measuring the work of adhesion of microstructures using the atomic force microscope (AFM) is proposed. The adhesive force acting between a sharp probe and a sample is obtained from the deflection of a micromachined cantilever, which is measured precisely by heterodyne interferometry with a sensitivity of 20 pN. The adhesive force was investigated using an Si/sub 3/N/sub 4/ probe with a tip radius of 50 nm for an SiO/sub 2/ substrate and five kinds of solution: H/sub 2/O, C/sub 2/H/sub 5/OH, CH/sub 3/COCH/sub 3/, CCl/sub 4/, and KOH. The measured forces range from 10 to 100 nN. The force measured for CH/sub 3/COCH/sub 3/ is the smallest. This is consistent with the finding that the rise with CH/sub 3/COCH/sub 3/ reduces the pinning influence of the surface-micromachined structures. The effect of the surface roughness and the contact area on the adhesive force is examined, and the results are discussed in terms of macroscopic adhesive theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>