Experimental evidence for two fundamentally different E' precursors in amorphous silicon dioxide

E' centers (trivalent silicons) in two silicate systems, thermally grown SiO 2 films on silicon and high surface area bulk sol-gel silicates, have been investigated. In the thermally grown silicon dioxide films, earlier work is extended by demonstrating that the hole trapping process is reversible; no complex structural rearrangement occurs at the hole trapping site (E' centers) after subsequent electron capture. This provides further evidence that these thermal oxide E' centers are oxygen vacancies as originally proposed by Feigl, Fowler and Yip. Also investigated is the radiation-induced generation of paramagnetic centers in high surface area sol-gel silicates containing various concentrations of the Raman active 608 cmi D 2 band attributed to strained cyclic trisiloxanes (three-membered rings). The results suggest a correlation between the concentration of the strained three-membered rings and the concentration of radiation-induced E' and paramagnetic oxygen centers, thus providing the first substantive evidence of the relationship between a specific strained siloxane structure and radiation damage in amorphous silicon dioxide. These results suggest the existence for (1) two different fundamental E' precursors and (2) a relationship between atomic level stress and the radiation damage process in amorphous silicon dioxide.