Size-dependent near-infrared photoluminescence from Ge nanocrystals embedded inSiO2matrices

We have succeeded in observing the size dependent photoluminescence (PL) from Ge nanocrystals (nc-Ge) with 0.9–5.3 nm in average diameter ${(d}_{\mathrm{ave}})$ in the near-infrared region. The nc-Ge were fabricated by rf cosputtering of Ge and ${\mathrm{SiO}}_2$ and post annealing at $800°\mathrm{C}.$ It was found that the sample with $d_{\mathrm{ave}}=5.3\mathrm{}\mathrm{nm}$ shows a PL peak at about 0.88 eV. With decreasing the size, the PL peak shifted to higher energies and reached 1.54 eV for the sample with $d_{\mathrm{ave}}=0.9\mathrm{}\mathrm{nm}.$ It was also found that the PL intensity increases drastically with decreasing the size. The observed strong size dependence of the PL spectra indicates that the observed PL originates from the recombination of electron-hole pairs confined in nc-Ge.