Atomic force microscopy and spectroscopy

Since it was invented by Binnig et al in 1986, atomic force microscopy (AFM) has played a crucial role in nano-scale science and technology. AFM is a microscopic technique imaging a surface topography by using attractive and repulsive interaction forces between a few atoms attached at a tip on a cantilever and a sample. In the case of attractive forces, there are three main contributions causing AFM. These are short-range chemical force, van der Waals force and electrostatic force. As the effective ranges of these forces are different, one of them is dominant depending on distance. Atomic force spectroscopy is the force-versus-distance measurement when using AFM. The atomic force can be detected by cantilever bending caused by a tip-sample interacting force, which is called static AFM. Also, the atomic force can be detected by using the resonant properties of a cantilever, which is called dynamic AFM. Under the on-resonance condition, the frequency, amplitude or phase of the cantilever will be shifted by the interaction force. While the force can be estimated in static AFM, for dynamic AFM it requires complicated formalism to evaluate the force from measured amplitude, phase or frequency data. Recently developed techniques for ultra-high resolution imaging unveil sub-atomic features of the sample, which are facilitated by low temperature, ultra-high vacuum environments together with a stiff cantilever. In this study, progress related to theoretical and experimental imaging and force spectroscopy will be discussed.