Effect of As doping on the photoluminescence of nanocrystalline 74Ge embedded in SiO2 matrix

Samples of nanocrystalline Ge-74 embedded in amorphous SiO2 film were prepared by Ge-74 ion implantation and subsequent primary thermal annealing. These samples were irradiated by neutron flux in a nuclear reactor then the second annealing followed. Irradiation with thermal neutrons leads to doping of nanocrystalline Ge-74 with As impurities due to nuclear transmutation of isotope Ge-74 into As-75. Transmission electron microscope, X-ray fluorescence, X-ray photoelectron spectroscopy, laser Raman scattering and photoluminescence of the obtained samples were measured. It was observed that with the increase in As-donors concentration, photoluminescence intensity first increased but then significantly decreased. An explanatory model of this non-monotonic behavior was discussed. (c) 2008 Elsevier B.V. All rights reserved.