Structural and optical properties of silicon-germanium alloy nanoparticles

Silicon-germanium alloy nanoparticles with spherical shape have been prepared by the thermal evaporation method. The shape and structure of these dots have been studied. Transmission electron microscopy images show that the SiGe nanoparticles grown at 100 Torr may be composed of two half-moon shaped sections. Furthermore from the transmission electron diffraction patterns and Raman spectra, a change of structure from amorphous to crystalline at the 0.4 Torr growth pressure was observed. It is also found that if the growth pressure increases, the Ge composition of SiGe dots will decrease. A model is proposed to explain this phenomenon.