Fig. 4

Shifts and intensity variations of peaks at ~ 3 eV. a Details from EEL spectra as shown in Fig. 2d, peaks ii and iii. When studying the monochromated LL-STEM-EELS at the ~ 3 eV energy-loss, it was found that we are observing two distinct peaks- one centred at around 2.85 eV and one peak with a maximum shifting from about ~ 3.2 to 3.5  eV when comparing the spectra from the edge (spectra 4 and 5) to the inside of the flakes (spectra 12, top spectrum here). b Map of the peak position of the higher energy-loss feature, as found by curve fitting to the peak maxima for all the peaks between 1.5 and 3.8 eV and tracking the position of the ~ 3 eV feature between 3–3.8 eV (scale: from black = 3.2 eV to white = 3.7 eV). c HAADF STEM image and map of the peak intensity of the 2.85 eV feature (peak ii) and the 3.2–3.8 eV feature (peak iii, tracked) as found by curve fitting to the peak maxima for all the peaks between 1.5 eV and 3.8 eV (intensity scale=arbitrary units). Both maps showed slightly enhanced intensity in the region of the first and the second terrace, the thinner region of the flake. In addition, the intensity of the 3.2–3.8 eV feature (peak iii, tracked) was found to be greatly enhanced at the edge of the flake as well as slightly enhanced at the step. Qualitatively, both peaks ii and iii follow a similar intensity distribution