Electrostatic and van der Waals forces in the air contact between the atomic force microscope probe and a conducting surface

Electrostatic and van der Waals forces of interaction between commercial probes of atomic force microscopes (AFMs) and conducting surfaces under atmospheric conditions are measured using contact atomic force microscopy. An algorithm of statistical processing of the initial photocurrent-displacement dependences is developed, which makes it possible to transform these dependences into the force-distance dependences. The Hamaker constant at the platinum (probe)-graphite (sample) contact is determined. It is shown that the measurement of electrostatic forces makes it possible to determine geometrical parameters of the AFM probe and to independently calibrate the stiffness of the cantilever.