ARTIFACTS IN FORCE MEASUREMENTS WITH THE ATOMIC-FORCE MICROSCOPE DUE TO DIGITALIZATION

The atomic force microscope has become a standard tool to measure surf ace forces, Force-versus-distance curves taken with an atomic force mi croscope often show a hysteresis in the noncontact region between appr oach and retraction. The hysteresis can be caused by the discrete, ste pwise motion of the sample due to digitalization, Since in the presenc e of liquids cantilever and sample are coupled, the cantilever oscilla tes 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. E specially when attractive forces are measured, cantilever oscillations can severely change the results.