In situ observation of the formation of Fe3O4 in Fe4N (001) due to electron irradiation.

γ'-Fe 4 N was subjected to electron irradiation with the dose rate of 6.8 X 10 2 3 e m - 2 s - 1 in a 400 kV transmission electron microscope. The first in situ observation of the formation of Fe 3 O 4 (O) on Fe 4 N (y') withthe orientation relationship of {100} O II {100} γ ' and O II γ ' has been made inside the microscope with the basic column vacuum of (5-6) × 10 - 5 Pa. A mechanism is proposed involving the electron-stimulated dissociation of Fe-N chemical bonds, desorption of nitrogen from the surface, adsorption of oxygen to the surface, and the oxidization of excessive metallic iron on the surface.