Effects of high pressure thermal treatments in oxygen and helium atmospheres on amorphous silicon dioxide and its radiation hardness

The effects of thermal treatments at similar to 400 degrees C in oxygen or helium atmospheres at similar to 180 baron the radiation hardness of amorphous SiO2 are studied. The generation efficiency of several point defects under gamma irradiation is compared to that of the untreated material. All the effects on point defects generation here observed can be explained in terms of changes in the precursor sites. In particular it has been observed that the thermal treatments can change the precursors sites of point defects both through temperature and pressure related processes, not depending on the atmosphere, and through oxygen related processes creating oxygen excess sites. The presence of dissolved oxygen also inhibits some hydrogen related processes, as the generation of H(l) centers, probably by activating different reactions paths for hydrogen. (C) 2009 Elsevier B.V. All rights reserved.