Abstract
The structural characteristics of crystalline germanium nanoparticles prepared by an evaporation method were investigated by transmission electron microscopy and electron energy-loss spectroscopy. Fivefold multiply twinned particles with diameters as fine as 7 nm were found; the misfit angle caused by symmetry is compensated by lattice distortion without introducing lattice defects. It is clarified that both the quantum size effect and lattice distortion occur in particles with 12–20 nm diameter. Due to distortion, the unit cell volume of these particles is compressed to 94% of that for bulk, on average. It was also found that the diamond structure is stable when the particle diameter is as small as approximately 2 nm.