On the electric field distribution within the field ion microscope and near the surface of field emitters

The electric field distribution within a field ion microscope is determined numerically. Realistic geometries are considered and the specimen is given shape. It is found that neglect of geometric features which are as far as 10 5 tip diameters away from the specimen can yield inaccurate results. A 9 degrees variation in shank angle is shown to induce a 40% change in the field near the specimen which can alter the ion trajectories and significantly modify the specimen stress distribution.