Study on probe current dependence of the intensity distribution in annular dark field images

The intensity profile of atomic columns in annular dark field (ADF) images was quantitatively investigated for a silicon (001) crystal using a cold field emission source in an aberration corrected scanning transmission electron microscope. The intensity distribution at the atomic column in the annular dark field image was blurred by increasing the probe current from 10 to 40 pA, which was quantitatively well fit by a simulated distribution convolved by Gaussian envelopes with area proportional to the probe current. The blur of the ADF images was primarily determined by the size of the cold field emission source.