Translated into quantum mechanical terms, the electron wave functions of the tip and the sample being imaged can overlap strongly enough to give rise to strong repulsive forces. Thus, in the AFM, the tunneling current upon which the STM relies is replaced by the force between the tip and the sample. The instrument can be adapted to sense a range of forces, including attractive or repulsive, interatomic, electrostatic, and magnetic forces. These forces cause angstrom-size displacements of the cantilevered tip, movement which is recorded and translated into a topographic image. Clearly, the information derived from these microscopy studies is providing new insights.
Surfaces are critical in the performance and interaction of materials.
To improve performance and to create new materials, scientists study surfaces, attempting to learn what happens at an atomic level. Until the advent of the STM and AFM, surface science took place in a vacuum. Over the years, scientists have done these studies under vacuum and hoped they were still relevant to the real world. This has been a major impediment. However, the STM and AFM don't require a vacuum.