Field Ion Microscopy with an External Image Intensifier

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Abstract
The exposure time of field ion micrographs at normalized pressure and voltage represents a figure of merit for comparison of various intensifier systems. External image intensification with a commercial RCA tube reduces the exposure time by a factor of more than 104, allowing recording of helium ion images in 1/1000 sec and standard speed motion pictures of neon ion images. Fast field evaporating metals can now be observed dynamically, and gold and copper photographs are shown as examples. The intrinsic noise of the image intensifier is not disturbing. A flicker effect is observed in the helium ion image of a stable tungsten surface at 21 °K in the presence of a small amount of water vapor. The fluctuations depend upon the local field strength; they disappear with increasing field, increasing temperature, or with the addition of a trace of neon to the imaging gas. The flicker effect is probably due to desorption of water molecules by the impact of imaging gas atoms.

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