
71Introduction to Nanosensors
1.20.3 Other Forces and Potentials
The force between tip and sample is composed of many contributions: elec-
trostatic, magnetic, van der Waals, and chemical forces in vacuum. In ambi-
ent conditions, there are also meniscus forces. While electrostatic, magnetic,
and meniscus forces can be eliminated by equalizing the electrostatic poten-
tial between tip and sample, using nonmagnetic tips, and operating in vac-
uum, the van der Waals forces cannot be switched off. For imaging by AFM
with atomic resolution, it is desirable to lter out the long-range force contri-
butions and measure only the force components that vary ...