In the present work, we describe a technique to measure the tip-sample
interaction in a scanning force microscope setup with high precision.
Essentially, the force exerted on the cantilever is acquired simultan
eously with a spectrum of the cantilever. This technique is applied to
study the behavior of the microscope setup as the tip approaches a sa
mple surface in ambient conditions. The measured interaction can only
be understood assuming the formation of a liquid neck and the presence
of a thin liquid film on the tip as well as on the sample.