Field ion microscopy was invented by E. Muller in 1951. A field ion microscopy assembly is depicted in Fig. 1a. Its key elements include a specimen in the shape of sharp needle with positive potential of 1-10 keV applied to it and a fluorescent screen that has been replaced in modern assemblies by a microchannel plate, both placed in a vacuum chamber. The chamber is backfilled with an imaging gas, usually helium or neon, at pressure of 10^-5 to 10^-3 torr. The specimen is cooled to very low temperatures (~20–80 К).

The imaging technique is illustrated in Fig. 1b. Imaging gas around the tip is polarised in an electric field, and while the field is not uniform, polarised atoms are attracted to the needle surface. Adsorbed atoms may become ionised due to the tunnelling of electrons into the tip, and the ions are accelerated by the field in the direction of the screen, creating an image of the emitting surface on it. A field ion microscope’s resolution depends on the thermal speed of imaging ion and may reach 0.1 nm (i.e., atomic resolution) when the tip is cooled to very low temperatures (see Fig. 2).

Tip material limitations are the same as those of the field emission microscope. Hence, most research activities involving field ion microscopes are conducted on metals with high melting points (W, Mo, Pt, Ir). The most interesting results obtained using the field ion microscopy technique are associated with the study of the dynamical behaviour of surfaces and the behaviour of atoms on surfaces. The problems studied include adsorption and desorption, surface diffusion of atoms and clusters, step motion, equilibrium crystal shape, etc.