INFLUENCE OF INTERMOLECULAR INTERACTION FORCE ON THE JUMP MAGNITUDE OF THE ATOMIC FORCE MICROSCOPE PROBE DURING INDENTATION OF SOFT MATERIAL

摘要

When an atomic force microscope probe interacts with soft elastic material, it jumps at a distance exceeding 10 nm. It may seem that the probe crosses this distance through the air under the influence of the forces of intermolecular interaction, and only at the last moment it touches a surface of material. But this is a misconception. The paper considers analytical solutions of the probe interaction with hard and soft samples and analyzes possible probe jumps. At first, the paper considers the problem of the interaction of a parabolic probe with an absolutely rigid body. It was established that in this case the probe makes a jump comparable with the distance of one nanometer. The problem has either one or three solutions. Moreover, one solution is always physically unrealizable. Instead of reaching this solution, the probe stops on the surface of the body. If in the considered state of the probe three solutions are possible, then the second is stable and the third is unstable. An analysis of the probe interaction with soft material revealed that a larger part of the jump occurs inside the sample. In a number of problems, the probe motion in air can be neglected. The probe begins to jump at a distance of more than 10 nm at the moment of touching the soft material.