LOCAL ADHESIVE SURFACE-PROPERTIES STUDIED BY FORCE MICROSCOPY

Scanning force microscopy was used in the contact mode to determine th e adhesion force between a mica surface and a silicon nitride tip. The measurements were performed in an aqueous solution of sodium and calc ium chlorides. The adhesion force according to the Derjaguin-Landau-Ve rwey-Overbeek theory depends on the competition between two kinds of f orces: van der Waals and electrostatic ''double layer''. Two different curves of adhesion force versus salt concentration were obtained from the experiment with monovalent and divalent ions. The tip-surface adh esion force was determined from a statistical analysis of data obtaine d from the force vs. distance retracting curves.