Adhesion between nanoscale rough surfaces - II. Measurement and comparisonwith theory

In this investigation, the adhesion between particles and plates with root- mean-square, rms, surface roughness of 0.17-10.5 nm was measured by atomic force microscopy. Measurements obtained with particles both larger and smal ler than the surface asperities are presented. Results indicate adhesion fo rce decreases sharply with increasing surface roughness in the nanometer sc ale (<2 nm), followed by a gradual and slow decrease with further increase in roughness. Existing models were found to significantly underestimate adh esion force. Hence, a new model based on a geometry that considers both the height and breadth of asperities yielding an increased asperity radius com pared to previous approaches, as detailed in Part I of this series, is appl ied using both van der Waals and elastic deformation/work of adhesion based approaches. For the system studied in this investigation, the adhesion for ces predicted by the proposed model are considerably more accurate than tho se predicted by past models. (C) 2000 Academic Press.