1. Detecting the force of tip-surface interaction

The interatomic interaction force is detected by means of a spring with the tip at its end. The influence of tip-surface interactions on spring deflection is shown (figure 1 ).

In position A, the sample is at a great distance from the tip: the spring undergoes no deflection, as the interaction force is zero. When the sample is approached to a distance of around 10-100 nm from the tip, the spring is subjected to long-range forces such as Van der Waals, electrostatic or magnetic forces. Under the effect of attractive Van der Waals forces, for example, the spring will bend towards the surface. If we continue to move the sample vertically towards the tip, we observe a sudden jump from the tip to the surface (position B) when the tip-surface assembly is in air, which is generally the case....