Point defects in ≈7nm-sized fumed silica nanoparticles were studied by Q-band electron spin resonance following 10eV irradiation to photodissociate H from passivated defects. In studying the influence of vacuum annealing special attention was paid to the behaviour of the structure of the nanoparticles when brought into contact with ‘bulk’ Si/SiO2 entities at elevated temperatures in vacuum (Tan = 1005C), i.e., the presence of an Si/SiO2 interface. Alterations in the electron spin resonance characteristics of the observed intrinsic point defects were monitored. As indicated by the observed increase in E′ defect density and alterations in electron spin resonance properties it appears that the co-presence of the Si/SiO2 structure affects the fumed SiO2(x) network structure distinctly, which was ascribed to the reaction of SiO released at the Si/SiO2 interface. In addition to the vulnerability for SiO attack, it was also found that the surface and near surface layers of the nanoparticles respond differently to the presence of SiO during the anneal than the core region. Results were ascribed to the reaction with SiO released at the Si/SiO2 interface.

Paramagnetic Intrinsic Point Defects in nm-Sized Silica Particles - Interaction with SiO at Elevated Temperatures. K.Clémer, A.Stesmans, V.V.Afanasev: Materials Science and Engineering C, 2007, 27[5-8], 1475-8