  Crystalline Silicon-on-Sapphire (SOS) films were implanted with boron (B$^+$)
and phosphorous (P$^+$) ions. Different samples, prepared by varying the ion
dose in the range $10^{14}$ to 5 x $10^{15}$ and ion energy in the range
150-350 keV, were investigated by the Raman spectroscopy, photoluminescence
(PL) spectroscopy and glancing angle x-ray diffraction (GAXRD). The Raman
results from dose dependent B$^+$ implanted samples show red-shifted and
asymmetrically broadened Raman line-shape for B$^+$ dose greater than $10^{14}$
ions cm$^{-2}$. The asymmetry and red shift in the Raman line-shape is
explained in terms of quantum confinement of phonons in silicon nanostructures
formed as a result of ion implantation. PL spectra shows size dependent visible
luminescence at $\sim$ 1.9 eV at room temperature, which confirms the presence
of silicon nanostructures. Raman studies on P$^+$ implanted samples were also
done as a function of ion energy. The Raman results show an amorphous top SOS
surface for sample implanted with 150 keV P$^+$ ions of dose 5 x $10^{15}$ ions
cm$^{-2}$. The nanostructures are formed when the P$^+$ energy is increased to
350 keV by keeping the ion dose fixed. The GAXRD results show consistency with
the Raman results.
