Electron-Beam-Induced Surface Reduction in Transition-Metal Oxides

The effect of electron irradiation on the surfaces of several maximally-valent transition-metal oxides (TiO2, Nb2O5 V2O5 and WO3 ) has been studied directly inside the electron microscope using the techniques of surface profile imaging, selected area electron diffraction and electron energy loss spectroscopy. Irradiation causes the near-surface regions of these oxide crystals to become depleted of oxygen, and small crystals of the respective binary oxides, identified by their lattice spacings, accumulate on the surface. These (metallic) lower oxides usually have welldefined orientational relationships with the bulk oxide. It is concluded that electron microscopical methods should be highly useful for characterizing electron-stimulated-desorption processes occurring at surfaces.