Raman studies of silicon nanocrystals embedded in silicon suboxide layers

Raman spectroscopy is used for the study of SiO$_x$ ($x\approx$ 1) layers subjected to thermal annealing at the temperatures from 950 to 1200$^\circ$C to form Si nanocrystals inside the layers. From comparison of the experimental data with the model of spatial confinement of phonons, the volume fractions of the crystalline and amorphous Si phases in the layers are determined. It is established that, as the annealing temperature is increased, the average dimensions of Si nanocrystals increase from 4 to 6.5 nm. This is attributed to the coarsening of nanocrystals due to crystallization of the amorphous Si phase and to the processes of coalescence of neighboring nanocrystals at the highest temperatures of annealing.