Geometrical Analysis of Field - Ion Images

Field ion microscopy (FIM), transmission electron microscopy (TEM) and computer simulation techniques have been used to experimentally investigate the field ion image geometry. Electron micrographs and electron diffraction patterns were obtained from tungsten specimens after controlled amounts of field evaporation. From a knowledge of the changes in the image dimensions as a function of the variation in the tip radius and the tip profile from the electron micrographs, an attempt has been made to define the projection point and the ion trajectory. The information has been used to obtain computer simulated patterns and the results are discussed.