On the heating of a field ion microscope specimen

The temperature distribution in a field ion microscope (FIM) specimen heated simultaneously by thermal radiation, the imaging gas, and an energetic beam of charged particles was calculated in the steady-state approximation employing a realistic model for the FIM specimen. The variation in crosssectional area of the specimen with distance along the shank was taken into full account. The possibility of a temperature change caused by the thermoelastic effect was also considered and shown not to be of importance. The value of δT max (maximum temperature difference along the length of the specimen) was ∼ 2.5 × 10−3 °K at the best image field (4.4 v Å−1) for tungsten imaged at 15°K with helium gas. Hence, it was concluded that the act of observing a specimen by field ion microscopy did not perturb appreciably the temperature of the tip. It was also shown that a rather high energy density beam of energetic particles was required to produce a significant value of δT max