Hey microscopy & EELS experts,

I have measured EELS on NiO in a TEM in the low-loss region (1-11eV, see attached), with a monochromated beam, 60kV, 0.15eV resolution. Spectra look more or less like I would expect them to do -- fundamental electronic excitation between 4-5eV is well visible, above that some higher order transitions, nothing out of the expected. HOWEVER: we see this massive peaky feature at ~9eV. I have looked at reference data from eelsdb.eu ( https://eelsdb.eu/spectra/nickel-oxide/ obtained on powder samples), and these do not contain such a peak.

We have three NiO samples that all have this feature; none without. When we look at the substrate (MgO) on the same lamellae, it just looks like MgO should, no peak at 9eV, so it must have something to do with NiO in particular.

Has anyone ever seen something similar, and/ or has any idea what we are looking at here?

Thank you.

Robert