The effect of Si-substrate on the optical characterization of Ge nanostructures obtained by LPCVD

Germanium nanostructures (Ge-ns) were grown by Low Pressure Chemical Vapor Deposition on a SiO₂ film. Samples were studied by micro-Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). We report the analysis of the influence of the silicon substrate on the Raman scattering spectra of the Ge-ns. Both the broadening and the small shift observed in the Raman peak can be attributed to the variation in the size distribution of the Ge-ns and the phonon confinement. AFM images show a Ge-ns density around 4×10¹⁰ cm^-2, with a 20 nm mean size and 6 nm height. AFM and SEM images revealed an excellent agreement which could be used to estimate the size and size distribution of the nanostructures. Finally, the Raman spectra were fitted with a theoretical model to evaluate the average size and full-width at half-maximum.