In both field ion microscopy and scanning tunneling microscopy, the preparation of sharp tips is crucial for carrying out observations with atomic resolution. The demands on the tip in scanning tunneling microscopy are not too rigorous; it has to have a sharp region of some kind in order to probe a surface with high resolution. For this task, tips are available commercially. In field ion microscopy, the tip is the surface to be studied, and therefore has to have a well-formed overall shape. As already pointed out in Chapter 2, there are fairly standard methods for preparing and polishing wire samples to the proper shape. We will give a few examples of how this can be accomplished. With the exception of the description for rhodium, these were all worked out by Liu, and with some minor changes taken directly from his thesis, but it should be noted that other recommendations are available.

Preparation of samples for field ion microscopy

“Three conditions have to be met for a good field emitter specimen: (a) The end of the specimen, that is the tip, has to be sharp enough so that strong electric fields can be attained at reasonable voltages; (b) The tapered section, or shank, has to be smooth and devoid of large defects or undercuts, so that the emitter can withstand field stresses; and (c) The whole shank and tip should be smooth and symmetric to avoid serious distortion of the image.