The .Si identical to Si₃ defect at various (111)Si/SiO₂ and (111)Si/Si₃N₄ interfaces

The low-temperature (2<or=T<or=45 K) X- and K-band electron spin resonance (ESR) properties of the Si/SiO₂ interfacial (111) P_bO defect-identified with .Si identical to Si₃ and with the unpaired sp³ hybrid along (111)-as localised at three 'different' (111)Si/SiO₂ interfaces, are comparatively surveyed. It is observed that differences in the ESR details develop in moving from state-of-the-art thermally oxidised Si/SiO₂ over a Si/SiO₂ structure grown under strongly reduced O₂ pressure to the Si/native oxide case, indicating increasing interfacial strain or disorder. Secondly, ESR data are presented on the first observation of the .Si identical to Si₃ defect-now called (111)P_bNO-in (111)Si/Si₃N₄, thermally grown at 1100+or-20 degrees C in NH₃. The main ESR signatures of the P_bO and P_bNO centres are very similar, from which their common origin is concluded. Yet, the differences in ESR properties from state-of-the-art Si/SiO₂ to the Si/native SiO₂ structures are all exhibited by P_bNO too; in fact, they show up more intensely and reveal the more strained nature of the Si/Si₃N₄ interface. The P_bNO observation confirms the P_bO(P_bNO) defect as a prototype dangling-bond defect with the unpaired hybrid pointing out of the Si substrate. Generally, the P_bO(P_bNO) defect appears to be a highly sensitive probe apt to reflect variations in the physico-chemical nature of the interface through its low-temperature ESR features.