What is an Atomic Force Microscope (AFM)?
Atomic Force Microscope (AFM) is a new experimental technique for observing the microscopic surface topography of samples by utilizing the interaction forces between atoms and molecules. It is equipped with a nanoscale probe fixed on a flexibly controllable microscale elastic cantilever. When the probe approaches the sample, the interaction force between atoms at the probe tip and atoms on the sample surface bends the cantilever and displaces it from its original position. A three‑dimensional image is reconstructed according to the deflection or vibration frequency of the probe during scanning, so that the surface morphology and atomic composition of the sample can be obtained indirectly.
It studies the surface structure and properties of materials by detecting the extremely weak interatomic force between the sample surface and a miniature force‑sensitive element. One end of a microcantilever, which is highly sensitive to tiny forces, is fixed, while the microtip at the other end approaches the sample and interacts with it. The interaction force causes deformation or a change in the motion state of the microcantilever.
During sample scanning, sensors detect these changes to obtain the distribution of interaction forces, and thus surface structural information with nanoscale resolution. An AFM mainly consists of a cantilever with a sharp tip, a cantilever motion detector, a feedback loop for motion control, a piezoelectric ceramic scanner for sample scanning, and a computer‑controlled system for image acquisition, display and processing. The motion of the microcantilever can be detected by electrical methods such as tunneling current detection, or optical methods including beam deflection and interferometry. When the tip is sufficiently close to the sample and short‑range repulsive forces exist between them, detection of this repulsion enables surface imaging at atomic resolution; the resolution is generally at the nanometer level. AFM measurement imposes no special requirements on samples and can be applied to solid surfaces, adsorbed systems and more.
