Depassivation kinetics in crystalline silicon nanoparticles

The formation of silicon dangling bond (Si-db) defects in crystalline silicon nanoparticles (Si-NPs) is studied by electron paramagnetic resonance combined with vacuum-annealing experiments. The kinetics of Si-db formation due to H desorption is found to be reliably described by a first-order-rate thermal model with a mean activation energy E_d=2.25 eV and a spread σ_Ed=0.28 eV in the activation energy distribution. These values deviate from those reported in previous studies of other Si-based materials, which is attributed to the presence of different interfacial hydrides Si _4-n-Si-H_n. Hence, the generation Si-db defects in Si-NPs initiates at a much lower temperature than one would expect based on the previously reported kinetics parameters. Unlike the case of planar Si/SiO ₂ interfaces, no permanent interface degradation is observed upon annealing of Si-NPs at temperatures â‰600 ^â̂̃C. This, together with the observation of an interfacial Si-db density similar to that typically incorporated in high quality thermally-grown SiO₂ on bulk silicon, indicates the formation of a rather relaxed and thermally stable surface oxide shell during natural oxidation of Si-NPs.