Low-loss region of MgO. The optical gap of 7.77 eV can be seen directly as the step increase. The exciton at the edge onset is not well-resolved. The peak at ~12 eV is also excitonic in nature. The intensity in the optical gap region below 8 eV is from transition radiation. In thicker samples this can produce small peaks from TE waveguide modes, and is suppressed in very thin samples.
By: Judy Cha
Microscope: FEI Tecnai T20
Energy Resolution: <0.2eV