Si-Nanocrystals with Bimodal Size Distribution in Evenly Annealed SiO Revealed with Raman Scattering

The size distribution of Si-nanocrystals (Si-ncs) in evenly annealed SiO is investigated with transmission electron microscopy (TEM), x-ray diffraction (XRD), and Raman scattering. Two groups of Si-ncs with very different most probable diameters are identified, where one is >6 nm and the other one is < 2 nm. Both of them increase gradually with increasing annealing temperature. Such a phenomenon is observed directly by TEM for samples with larger Si−ncs (>10 nm) and it can be revealed clearly for all samples by Raman spectra with two components (∼500 cm⁻¹ and ∼520 cm⁻¹). The results of XRD show the average effect. The experimental results indicate that the common assumption of Si-nc size distribution with single most probable diameter is not always proper and the possible mechanisms are briefly discussed.