On the formation and photoluminescence of Si(1-x)Ge(x) nanoparticles

Si(1-x)Ge(x) nanoparticles were prepared from two annealed alloy ingots at the compositions of Si:Ge = 9.5:0.5 and 9:1 using a vapor condensation technique under Ar atmosphere. These nanoparticles are all spherical, and increasing the working pressure leads to an increased particle size and size dispersion. Comparing to the alloy ingots, the nanoparticles have a higher average content of Ge. In addition, increasing the working pressure also causes the Si(1-x)Ge(x) nanoparticles to become more Ge-rich. This can be ascribed to the lower melting point and higher kinetic energy of Ge than Si during the evaporation process. The photoluminescence of Si(1-x)Ge(x) nanoparticles ranges from visible light to infrared region, and the luminescence peak exhibits a red shift as the Ge content in the nanoparticles increases. This indicates that the incorporation of Ge into Si has a dominant effect in the radiative recombination process, in comparison with the constant luminescence peak position in the case of pure Si nanoparticles with similar size distribution.