An experimental study on the adhesion at a nano-contact

Nano-adhesion characteristics between scanning probe microscope (SPM) tips of various radius of curvature and flats of different materials were experimentally studied. Adhesion and friction forces between Si-wafer (100) and Si3N4 tips were measured under various applied normal loads, and the results were compared to those of diamond-like carbon (DLC), tungsten incorporated diamond-like carbon (W-DLC) and octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) formed on Si-wafer surfaces. Also in order to study the effect of capillary force, tests were performed in various relative humidity. Results showed that the adhesion increased with the tip radius. When the applied normal load increased from 0 to 40 nN, the adhesion did not change, but the friction increased linearly. Results generally showed that surfaces of the more hydrophobic property revealed the lower adhesion. The adhesion forces increased with the relative humidity. The nano-adhesion phenomenon was discussed on the basis of JKR model and capillary force exerted by meniscus. (C) 2003 Elsevier Science B.V. All rights reserved.