Interpretation of force curves in force microscopy

A plot of the force interaction between two surfaces-typically a tip mounted on a cantilever beam and a flat surface-as a function of relative tip-sample separation constitutes a force curve, and such measurements have been termed 'force spectroscopy' (FS). The authors describe how to interpret force curves so as to gain information about: (i) the instant of tip-sample contact, (ii) the magnitude and functional dependence of adhesive and long-range attractive forces for different tip/sample combinations, (iii) possible mechanisms of long-range force interaction (surface layers, fixed dipoles, patch charges), (iv) tip-sample contact area, which relates to the imaging mechanism in contact-mode force microscopy, (v) the elastic modulus and plasticity of thin and thick films, and (vi) how the pull-off force varies as a function of the maximum load.