Effect of Size of Ge Nanocrystals Embedded in SiO2 on Raman Spectra

In this paper, we investigate the effect of Ge nanocrystal size on the Raman results. The Ge nanocrystal size distributions of samples rapid thermally annealed at 800 and 1000 °C for 300 s were obtained from the TEM pictures. We constructed the theoretical Raman spectrum based on the phonon confinement model taking into account of the size distribution of the nanocrystals. By taking into account of the Ge nanocrystal size distribution, we found a good fit between the experimental and theoretical Raman results at the lower wavenumber portion from the Raman peak for samples annealed at 800 and 1000 °C. Our model, however, is not able to account for the portion in the Raman spectra above the Raman peak. We suggest that stress in the annealed films maybe responsible for this discrepancy.