Oxygen depletion in electron beam bombarded glass surfaces studied by XPS

XPS has been utilized to study the compositional changes which occur in glass after electron beam irradiation. In the bombarded surfaces a reduction in Na and O signals is observed, while Ca signal shows negligible variations. Two O_1s signals, assigned to bridging and non-bridging oxygen were found. Irradiation causes a decrease of these two types of oxygen. This is at variance with Lineweaver's mechanism which accounts for the decrease of the non-bridging oxygens only. After irradiation a second component in the Si_2p line is found. It has been attributed to the formation of SiSi bonds induced by oxygen outgassing. The formation of these bonds leads to a more compact structure and this might explain the observed density change in irradiated glass.