Origin of room temperature broadband light emission and carrier dynamics in Ag ion-implanted silicon nanocrystals

We studied the origin of broad band light emission in the Ultraviolet (UV) to the red from silicon nanoparticles fabricated using a single low energy (32 keV) silver ion implantation with a fluence of 5*10¹⁵ ions/cm² in crystalline Si. It is found from a systematic study of the annealing carried out at certain temperatures that the spectral characteristics in the UV and blue region remains unchanged except for the enhancement of light emission intensity due to annealing. The annealing results in nucleation of Ag nanoclusters in the vicinity of Si nanoparticles which enhances the emission intensity. Time-resolved photoluminescence (TRPL) measurement demonstrates that the emission originates from both highly localized defect bound excitons at the nanoscale Si interface, as well as surface and interface traps associated with the increased surface area of the Si nanocrystals. The emission in the UV is due to interband transitions from localized excitonic states at the interface of Si/SiO₂ or from the surface of Si nanocrystals. The radiative efficiency of the UV and the green emission from the Si nanoparticles can be modified by the localized plasmons interaction induced by the nucleation of Silver nanoparticles on controlled annealing of the samples. Broadband emission ranging from the UV to the red wavelength range can be obtained on Ag implanted onto a single silicon substrate.