flat surface, atomically sharp features on the (305) face of SrTi03 [61], or the

One of the advantages of using point probe experiments in adhesion studies is that the requirements to the surface quality in order to achieve molecularly smooth contact are reduced by virtue of nanometer size dimensions of the contact. Contact mechanics predicts that pull-off forces in CFS are directly proportional to effective radius defined by equation (1). One can immediately recognize, however, that substrate roughness, e.g., local variations in the substrate radius of curvature will affect the magnitude of adhesion. For example, analysis of force and topography maps from AFM measurements on a chemically homogeneous, hydrophobic sample, silanized etched silicon [63], showed unambiguous direct correlation between substrate's local curvature and the force of adhesion (Fig. 6). Performing CFS on a HS(CH2)i5COOH/HS(CH2)i5COOH pair in ethanol, McKendry et al observed [64] a greater than a factor of two reduction in the width of adhesion force distribution when they switched from polycrystalline Au substrates to predominantly single crystalline annealed Au on mica substrates. A similar observation was made in the work of Fujihira and co-workers [65], who measured adhesion in water and used