EFFECT OF SCANNING FORCE MICROSCOPE SCANNER GEOMETRY ON PROBE-SAMPLE CONTACT FORCE

In a scanning force microscopy (SFM, or atomic force microscopy) syste m, a simultaneous recording of the probe cantilever deflection and the corresponding probe-sample distance yields a so-called force-distance curve. When the SFM probe is away from the sample surface, there is n o significant interaction between the probe and the sample and hence t he deflection angle is constant. This results in a zero force change i n the force-distance curve. However, in SFM probe-scanning geometry as opposed to sample scanning, a nonzero force change in a force-distanc e curve before probe-sample contact is usually observed. This article discusses the reasons for this phenomenon and its implications for con tact mode SFM imaging and complementary measurements. It is found that such a slope is directly related to the minimum probe-sample contact force and the force uniformity that the microscope can achieve during contact imaging. Possible solutions, including a ''variable set-point' ' scheme, are proposed. (C) 1997 American Institute of Physics.