A method is provided for forming a rare earth element-doped silicon oxide (SiO.sub.2) precursor with nanocrystalline (nc) Si particles. In one aspect the method comprises: mixing Si particles into a first organic solvent, forming a first solution with a first boiling point; filtering the first solution to remove large Si particles; mixing a second organic solvent having a second boiling point, higher than the first boiling point, to the filtered first solution; and, fractionally distilling, forming a second solution of nc Si particles. The Si particles are formed by immersing a Si wafer into a third solution including hydrofluoric (HF) acid and alcohol, applying an electric bias, and forming a porous Si layer overlying the Si wafer. Then, the Si particles are mixed into the organic solvent by depositing the Si wafer into the first organic solvent, and ultrasonically removing the porous Si layer from the Si wafer.