Raman scattering in InSb spherical nanocrystals ion-synthesized in silicon-oxide films

The Raman spectra of SiO$_2$ films containing InSb spherical nanocrystals produced by ion-beam synthesis are studied. TO- and LO-like modes in the spectra of the InSb nanocrystals are detected at frequencies of 187 and 195 cm$^{-1}$, respectively. The shift of these modes to high frequencies with respect to the corresponding frequencies in InSb bulk crystals is analyzed from the viewpoint of the influence of the quantum-confinement effect, strains in nanocrystals, the surface phonon frequency, and scattering at the frequency corresponding to stretched anion–cation modes at the surface of polar spherical nanocrystals. The position of the 195-cm$^{-1}$ mode corresponds to LO phonons in InSb nanocrystals hydrostatically compressed in the SiO$_2$ matrix at pressures of about 10 kbar. The 187-cm$^{-1}$ mode corresponds to resonance at the Fröhlich frequency.