Further evidence on the observation of compositional fluctuation in silicon-germanium alloy nanocrystals prepared in anodized porous silicon-germanium films

The microstructure of porous anodized silicon-germanium (Si1−xGex) films was characterized using Raman spectroscopy and electron microscopy. Different porosity samples were obtained from undoped (high-resistivity) epitaxial Si0.87Ge0.13 films and from single-crystalline and low-resistivity Si0.90Ge0.10 wafers. Supporting the earlier observations (on the former type of porous samples) we reported recently, the Raman results presented in this study convincingly demonstrate that as the film porosity increases, the sizes of Si1−xGex nanocrystals decrease and the film composition modifies in favor of Ge. Structure and the scale of the SiGe nanoparticles in these films were shown and examined by high-resolution (HR) electron microscopy.