70Ge nanocrystals in SiO2 films under neutron irradiation: A Raman and photoluminescence study

Abstract 70 Ge isotopic nanocrystals embedded in SiO 2 films were prepared by ion-implantation and neutron irradiation. Laser Raman scattering (LRS) and photoluminescence (PL) spectra were employed to characterize the samples. After 70 Ge + ions with the dose of 3 × 10 16  cm −2 and the energy of 150 keV were implanted with subsequent annealing, the Raman peak of 70 Ge nanocrystals is shown at around 305 cm −1 due to isotopic effect. It blueshifts to higher wave numbers and the FWHM becomes narrower with increasing annealed temperature. However, The PL peak at 565 nm from nanocrystals is not exhibited before neutron irradiation due to the quenching of the GeO 4 tetrahedra, instead of GeO 2 due to Ge insufficiency. A Raman peak position 262 cm −1 corresponding to GeO 4 tetrahedra, was formed after ion-implantation and could be annihilated by neutron irradiation and subsequent annealing, which help improve the luminescent property of Ge nanocrystals.