Characterization of Sn and Si nanocrystals embedded in SiO2 matrix fabricated by magnetron co-sputtering

Sn and Si nanocrystals were prepared by depositing Sn-Si-rich SiO2 films using a co-sputtering process and a subsequent annealing. The microstructure and optical properties of Sn and Si nanocrystals were characterized by scanning electron microscopy (SEM), Raman spectra, X-ray diffraction and photoluminescence spectra. The crystallization of Sn has started at the annealing temperature of 400 °C, and was accomplished at 700 °C. However, the phase of amorphous Si starts to transform into nanocrystal Si when the annealing temperature is higher than 700 °C. These results illustrate that Sn existence as an element may played an important role in lowering the crystallization temperature of Si, and the crystallization rate of Si will be enhanced when Sn atom serves as the nucleation centre. Because quantum confinement effects are expected at relatively large radius for nanocrystal Sn, the redshift of high-energy PL peak may result from quantum confinement effects of nanocrystal Sn. However, the low-energy PL peak may be attributed to defects.