EFFECTS OF ELECTRON-BOMBARDMENT ON THE SURFACE-COMPOSITION OF WO3, OXIDIZED W AND TA FOILS

By using both Auger electron spectroscopy and electron-stimulated desorption measurement techniques, electron-beam-irradiation-induced oxide reduction has been observed on WO3 and Ta2O5. In both cases, the light element (oxygen) is preferentially removed which in turn leaves the specimens' surface enriched with the metal element. In addition, visible darkening in the beam-illuminated area provides evidence of beam-irradiation-induced oxide reduction and irradiation-enhanced diffusion effects. Measurements of Auger electron intensities from the composition altered overlayer indicate that the beam-irradiated overlayer consists of nearly equal parts of metal and oxygen atoms upon extended electron bombardment. The observed changes in the surface composition of contaminated specimens also show additional beam effects like induced out-diffusion and beam-induced desorption. A brief comparison with the published results concerning ion irradiation on the corresponding specimens is also included.