Structural and optical properties of germanium nanoparticles

Germanium nanoparticles with spherical shape have been prepared by the thermal evaporation method. The shape and structure of these particles have been studied. Transmission electron microscopy images show that a change of Ge structure from amorphous to crystalline occurs at a growth pressure of 0.4 Torr and is attributed to the change of lattice constant. When the growth pressure becomes larger than 0.4 Torr, a fractallike tree structure made of Ge nanoparticles is observed. As the pressure increases further, the dot shape becomes clearer and many dots overlap. From the Raman spectra, it is found that the diamond structure is dominant for Ge dots.