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Abstract

The atomic force microscope has become a standard tool to measuee surface forces. Force-versus-distance curvss taken with an atomic force microscope often show a hysteresis in the noncontact region between approach and retraction. The hysteresis can be caused by the discrete, stepwise motion of the sample due to digitalization. Since in the presence of liquids cantilever and sample are coupled, the cantilever oscillates after each step. Depending on when a data point is recorded during this oscillation, the amplitude of the cantilever deflection measured may deviate from the equilibrium value. This might cause a hysteresis and other misleading results in force-versus-distance measurements. Especially when attractive forces are measured, cantilever oscillations can severely change the results