Figure 4. Effect of varying helium mean beam energy on sample contrast.

(a–e) 83, 72, 66, 42, and 21 meV SHeM micrographs of the 15-nm-thick gold on silicon sample. All images were taken with the sample at the specular position, with a 200 bar beam and the sample at room temperature (294 K). Insets show simulated images with Poisson noise added, according to the observed count rates. Note that the contrast is maintained in the simulations, but lost in the data, which confirms the presence of an additional contrast mechanism.