EELS fine structure analysis of radiation damage of V2O5
The oxides of maximum valence transition metals have been extensively studied in view of their useful physical and chemical properties. Vanadium pentoxide is one such compound which exhibits important catalytic properties, but is sensitive to electron beam irradiation. Vanadium pentoxide has the orthorhombic symmetry and the structure is built from deformed octahedra with a longer and weak V-O bond along the c direction. Consequently, V2O5 is a layered structure with (001) cleavage plane, and the oxygen atoms located at the cleavage plane can be easily lost during the electron beam irradiation. In this paper we present time resolved parallel detection EELS study of radiation damage of V2O5 with a 200 kV cold field emission analytical electron microscope (HF-2000). Samples of V2O3 and VO2 are also analyzed for comparison. The EELS spectra were obtained with a spectrometer dispersion of 0.1 eV per channel in TEM image mode using probe sizes of 20-50 nm. The beam current recorded by a picoammeter connected to the screen was calibrated by the direct measurement with a Faraday cup for the calculation of electron dosage.