Although the method of dosage identification established by the neural network cannot be known, the set of pixel intensity histograms in Figure 2 c provides some insight into the statistical differences among SEM images of chevrons milled with different ion beam settings: There is a clear trend toward higher pixel intensities (i.e., brighter images) with increasing dose, and a small peak at low pixel intensity emerges when the dose is high enough for the design to be milled through the full thickness of the gold film, exposing the silicon substrate (which appears black in SEM images).
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