Observation of a delocalizedE’ center in buried SiO2

The oxygen‐vacancy defect (E’) generated at the surface of buried SiO2 (BOX) layers of the separation by implantation of oxygen structure has been studied by K‐band electron spin resonance. Besides the usual Eγ’ signal, the Eδ’ center—a delocalized variant of the E’ center—has been identified in the BOX. No such signal, however, was observed in reoxidized (950 °C; 1.1 atm O2) BOX or conventional thermal oxide. These data lead to the proposal of an adapted model for the defect, based on the existence of small Si clusters (≳5 atoms) in the BOX serving as E’ defect precursors. This model implies that the buried oxide contains excess Si, exceedingly so near the BOX/substrate interface.