Spectroscopic investigation of quantum confinement effects in ion implanted silicon-on-sapphire films

TL;DR

This study investigates quantum confinement effects in ion-implanted silicon-on-sapphire films using Raman, photoluminescence, and X-ray diffraction, revealing nanostructure formation and size-dependent luminescence.

Contribution

It provides detailed spectroscopic analysis of how ion implantation induces silicon nanostructures and quantum confinement effects in SOS films, highlighting the influence of ion dose and energy.

Findings

Red-shifted and broadened Raman lines indicate phonon confinement.

Size-dependent visible luminescence at ~1.9 eV confirms nanostructure formation.

Nanostructures form at higher P+ ion energies, as shown by GAXRD.

Abstract

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.