Surface studies on refractory metals and alloys with the aid of the field ion microscope and atom probe

The field ion microscope is described as a tool in the investigation of the surface-specific properties of refractory metals and alloys, and some typical results of such studies are presented. Crystal lattice plane distances and occupancy densities for several crystal lattice planes with low Miller indices were determined for tungsten. Electron structure also influences the FIM image, since tungsten and molybdenum, both with bcc crystals, show significant differences in their FIM images. The detection of voids in alloys through the FIM image is illustrated. The basic idea of the channel plate image amplifier is mentioned. The modern interpretation of field ionization and FIM imaging on the basis of field induced adsorption of inert gases is discussed. The concept of the atom probe field ion microscope, which enables analysis of individual atoms and the composition of individual crystal lattice planes to be studied, is described.